Search

The body produces heme-derived bilirubin daily that needs to be detoxified to prevent hyperbilirubinemia. The bilirubin transferase enzyme system seems to be the only effective mechanism for clearing bilirubin from humans. Research on the Crigler-Najjar type-I disease has led to the critical characterizations of the bilirubin isoforms UGT1A1 HUG-Br1 and UGT1A4 HUG-Br2. Results of a study on the disruption of a hydrophobic microregion called MRA in the UGT1A1 bilirubin isoform and the structure-function link of a conserved diphenylalanine in this region are presented.

Hybrid nanoparticles (NPs) have attracted considerable attention because of their ability to provide diverse properties by integrating the inherent properties of multiple components; however, synthetic strategies to control their morphology remain unexplored. In this study, a new method was used to control the morphology and optical properties of Au-Ni heterostructure (ANH) NPs. Unique morphological changes were observed by varying the Au/Ni precursor ratio from 2:1 to 1:4, exhibiting a shape transformation from dumbbell-like to quasi-spherical owing to the Ni NP size expansion, whereas the Au NP maintained their size. Moreover, increasing the Ni ratio induced plasmonic band broadening and wavelength redshift, resulting in color changes from red to navy and black. In terms of the structure, the atomic orientation of the crystallite showed that even a large lattice mismatch can result in heterojunctions at the NPs. In addition, the reaction aliquots uncovered heterogeneous nucleation and growth of ANH NPs in the colloidal system, demonstrating Ni reduction on the preformed Au NP owing to the reduction in potential gap. This study provides new insights into controlling the morphology of hybrid NPs using colloidal synthesis and the design of optimized materials for various applications.

Chiral Pb-free metal-halide semiconductors (MHSs) have attracted considerable attention in the field of spintronics due to various interesting spin-related properties and chiral-induced spin selectivity (CISS) effect. Despite their excellent chemical and structural tunability, the material scope and crystal structure of Pb-free chiral MHSs exhibiting the CISS effect are still limited; chiral MHSs that have metal-halide structures of octahedra and tetrahedra are only reported. Here, we report a new class of chiral MHSs, of which palladium (Pd)-halides are formed in 1D square-pyramidal structures or 0D square-planar structures, with a general formula of (( R / S -MBA) 2 PdBr 4 ) 1- x (( R / S -MBA) 2 PdCl 4 ) x (MBA = methylbenzylammonium; x = 0, 0.25, 0.5, 0.75, and 1) for the first time. The crystals adopt the 1D helical chain of Pd-halide square-pyramid (for x = 0, 0.25, 0.5, and 0.75) and 0D structure of Pd-halide square-plane (for x = 1). All the Pd-halides are distorted by the interaction between the halide and the chiral organic ammonium and arranged in a noncentrosymmetric position. Circular dichroism (CD) for (( R / S -MBA) 2 PdBr 4 ) 1- x (( R / S -MBA) 2 PdCl 4 ) x indicates that chirality was transferred from chiral organic ammonium to Pd-halide inorganics. (( R -MBA) 2 PdBr 4 ) 1- x (( R -MBA) 2 PdCl 4 ) x ( x = 0, 0.25, 0.5, and 0.75) shows a distortion index of 0.127-0.128, which is the highest value among the previously reported chiral MHSs to the best of our knowledge. We also find that ( R / S -MBA) 2 Pd(Br 1- x Cl x ) 4 crystals grow along the out-of-plane direction during spin coating and have high c -axis orientation and crystallinity, and ( R / S -MBA) 2 Pd(Br 1- x Cl x ) 4 ( x = 0 and 0.5) crystals exhibit a CISS effect in polycrystalline bulk films. These results demonstrate the possibility of a new metal-halide series with square-planar structures or square-pyramidal structures for future spintronic applications.

Suppressing the dark current density ( J d ) while maintaining sufficient charge transport is important for improving the specific detectivity ( D *) and dynamic characteristics of organic photodetectors (OPDs). In this study, we synthesized three novel small-molecule acceptors (SMAs) densely surrounded by insulating alkyl side chains to minimize the J d in OPDs. Introducing trialkylated N-annulated perylene diimide as a terminal moiety to the alkylated π-conjugated core structure was highly efficient in suppressing J d in the devices, resulting in an extremely low J d of 4.60 × 10 -11 A cm -2 and 10-100 times improved D * values in the devices. In addition, SMAs with a geometrically aligned backbone structure exhibited better intermolecular ordering in the blended films, resulting in 3-10 times as high responsivity ( R ) values in the OPDs. Outstanding OPD performances with a D * of 8.09 × 10 12 Jones, -3 dB cutoff frequency of 205.2 kHz, and rising response time of 16 μs were achieved under a 530 nm illumination in photoconductive mode. Geometrically aligned core-terminal SMAs densely surrounded by insulating alkyl side chains are promising for improving the static and dynamic properties of OPDs.

Sepsis is a life-threatening condition with systemic inflammatory responses caused by bacterial infections. Considering the emergence of antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), sepsis is a great threat to public health. The gold standard methods for antimicrobial susceptibility testing (AST), however, take at least approximately 3 days to implement the entire blood culture, pure culture, and AST processes. To overcome the time-consuming nature of conventional AST, a method employing a chromatic biosensor composed of poly(diacetylene), alginate, and LB broth (PAL) is introduced in this study. Compared to the gold standards, AST with PAL biosensors can be completed within a time frame as short as 16 h. Such a significant reduction in time is possible because the consecutive cultures and AST are carried out simultaneously by encapsulating the bacterial nutrients and detection molecules into a single component. The bead-like hydrogel sensors were used in their freeze-dried form, which endows them with portability and stability, thus making them adequate for point-of-care testing. The PAL biosensor yields minimum inhibitory concentrations comparable to those from the Clinical and Laboratory Standards Institute, and the applicability of the biosensor is further shown in MRSA-infected mice.

When the skin is exposed to ultraviolet radiation (UV), it leads to the degradation of the extracellular matrix (ECM) and results in inflammation. Subsequently, melanocytes are triggered to induce tyrosinase-mediated melanin synthesis, protecting the skin. Here, we introduce a proactive approach to protect the skin from photodamage via the topical delivery of Streptomyces avermitilis -derived tyrosinase (SaTy) using single-walled carbon nanotube (SWNT). Utilizing a reverse electrodialysis (RED) battery, we facilitated the delivery of SaTy-SWNT complexes up to depths of approximately 300 μm, as analyzed by using confocal Raman microscopy. When applied to ex vivo porcine skin and in vivo albino mouse skin, SaTy-SWNT synthesized melanin, resulting in 4-fold greater UV/vis absorption at 475 nm than in mice without SaTy-SWNT. The synthesized melanin efficiently absorbed UV light and alleviated skin inflammation. In addition, the densification of dermal collagen, achieved through SaTy-mediated cross-linking, reduced photoinduced wrinkles by 66.3% in the affected area. Our findings suggest that SWNT-mediated topical protein delivery holds promise in tissue engineering applications.

To overcome significantly sluggish oxygen-ion conduction in the electrolytes of low-temperature solid-oxide fuel cells (SOFCs), numerous researchers have devoted considerable effort to fabricating the electrolytes as thin as possible. However, thickness is not the only factor that affects the electrolyte performance; roughness, grain size, and internal film stress also play a role. In this study, yttria-stabilized zirconia (YSZ) was deposited via a reactive sputtering process to fabricate high-performance thin-film electrolytes. Various sputtering chamber pressures (5, 10, and 15 mTorr) were investigated to improve the electrolytes. As a result, high surface area, large grain size, and residual tensile stress were successfully obtained by increasing the sputtering pressure. To clarify the correlation between the microstructure and electrolyte performance, a YSZ thin-film electrolyte was applied to anodized aluminum oxide-supported SOFCs composed of conventional electrode materials which are Ni and Pt as the anode and the cathode, respectively. The thin-film SOFC with YSZ deposited at 15 mTorr exhibited the lowest ohmic resistance and, consequently, the highest maximum power density (493 mW/cm 2 ) at 500 °C whose performance is more than five times higher than that of the cell with YSZ deposited at 5 mTorr (94.1 mW/cm 2 ). Despite the basic electrode materials, exceptionally high performance at low operating temperature was achieved via controlling the single fabrication condition for the electrolyte.

Ternary metal oxides are crucial components in a wide range of applications and have been extensively cataloged in experimental materials databases. However, there still exist cation combinations with unknown stability and structures of their compounds in oxide forms. In this study, we employ extensive crystal structure prediction methods, accelerated by machine-learned potentials, to investigate these untapped chemical spaces. We examine 181 ternary metal oxide systems, encompassing most cations except for partially filled 3d or f shells, and determine their lowest-energy crystal structures with representative stoichiometry derived from prevalent oxidation states or recommender systems. Consequently, we discover 45 ternary oxide systems containing stable compounds against decomposition into binary or elemental phases, the majority of which incorporate noble metals. Comparisons with other theoretical databases highlight the strengths and limitations of informatics-based material searches. With a relatively modest computational resource requirement, we contend that heuristic-based structure searches, as demonstrated in this study, offer a promising approach for future materials discovery endeavors.

The optimum composition ratio of the anode cermet (Ni-GDC) for solid oxide fuel cells (SOFCs) varies because the electron-collecting mechanism is different depending on its applications. A Co-sputtering method facilitates ratio control with sputtering power adjustment. However, there is a practical issue with fabricating anode cermet with various ratios attributed to the large sputtering yield gap of the metal target, Ni, and the ceramic target, gadolinia-doped ceria (GDC). Therefore, in this study, a Gd-Ce metal alloy was applied instead of GDC to match the sputtering rate with that of Ni, which enables a wide ratio range achievement. A thin film of Gd-Ce oxidized after deposition and successfully transformed to crystallized GDC under a SOFC operation environment. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) confirmed its crystallinity, and the film deposited with various power ratios was sputtered on the ScSZ electrolyte pellet to clarify the optimum Ni-GDC ratio for thin-film SOFCs. Last, the Ni-GDC was applied to anodized aluminum oxide (AAO)-supported SOFCs to maximize the performance. The performance change according to the thickness of Ni-GDC was identified, and the best performance among them was 638 mW/cm 2 at 500 °C.

Surface modification to improve the oxidation stability and dispersibility of MXene in diverse organic media is a facile strategy for broadening its application. Among the various ligands that can be grafted on the MXene surface, oleylamine (OAm), with amine functionalities, is an advantageous candidate owing to its strong interactions and commercial viability. OAms are grafted onto MXene through covalent bonds induced by nucleophilic reactions and H bonds in liquid interface reactions at room temperature. In addition, this grafting behavior of the ligand was characterized by a reduction in the slope with an increase in the ligand concentration ( C l ), confirming that the OAms were grafted via Langmuir-like behavior, and the monolayer of OAms was developed via two distinct steps (I: lying-down phase; II: ordered monolayer). MXene nanosheets modified by OAm (OAm-MX) are highly dispersible in a wide range of organic solvents owing to the alkyl chain of the OAms, which induces hydrophobic properties on the surface of MXene. The OAm-MX dispersion exhibits outstanding oxidation and dispersion stability and remarkable coating performance on a wide range of substrates owing to their excellent solution processability. Therefore, this study provides fundamental insights into the adsorption behavior and interaction between amine ligands and MXene nanosheets for the surface chemistry of MXene.

Understanding the dynamics of colloidal nanoparticles (NPs) in a solution is the key to assembling them into solids through a solution process such as electrophoretic deposition. In this study, newly developed in situ analysis with light scattering is used to examine NP dynamics induced by a non-uniform electric field. We reveal that the symmetric directions of moving NP aggregates are due to dielectrophoresis between the cylindrical electrodes, while the actual NP deposition is based on the charge of NPs (electrophoresis). Over time, the symmetry of the dynamics becomes less evident, inducing feeble deposition as the less-ordered dynamics become stronger. Eventually, two separate deposition mechanisms emerge as the deposition rate decreases with the change in the NP dynamics. Furthermore, we identify the vortex-like NP motion between the electrodes. These in situ analyses provide insights into the electrophoretic deposition mechanism and NP behavior in a solution under an electric field for fine film construction.

A strong interparticle connection needs to be realized to harvest unique nanoscale features of colloidal nanoparticles (NPs) in film structures. Constructing a strong contact and adhesion of NPs on a substrate is an essential process for improved NP film properties, and therefore, its key factors should be determined by understanding the NP deposition mechanism. Herein, we investigated the critical factors leading to the robust and strong adherence of the film structure and revealed that the NP deposition mechanism involved the role of surfactant ligands during electrophoretic deposition (EPD). The high amount of surfactant ligand treatment results in a high deposition rate of NPs in the early stage; however, the ligand treatment does not influence the deposition rate in the later stage. Furthermore, the deposition mechanism is found to involve three steps during EPD: island formation, lateral growth, and layer-by-layer deposition. Rapid NP deposition kinetics controlled by ligand treatments demonstrate the strong contact and adhesion of NP film structures; they are characterized by the fast charge transfer, low resistivity, and rigid NP layers of the Cu 2- x S NP-based devices. Finally, the controlled role of surfactant ligands in EPD enables design of high-performance nanostructured NP film devices with contact enhancement., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

We report the synthesis, characterization, and iodine capture application of a novel thorium-organic nanotube, TSN-626, [Th 6 O 4 (OH) 4 (C 6 H 4 NO 2 ) 7 (CHO 2 ) 5 (H 2 O) 3 ]·3H 2 O. The classification as a metal-organic nanotube (MONT) distinguishes it as a rare and reduced dimensionality subset of metal-organic frameworks (MOFs); the structure is additionally hallmarked by low node connectivity. TSN-626 is composed of hexameric thorium secondary building units and mixed O/N-donor isonicotinate ligands that demonstrate selective ditopicity, yielding both terminating and bridging moieties. Because hard Lewis acid tetravalent metals have a propensity to bind with electron donors of rival hardness (e.g., carboxylate groups), such Th-N coordination in a MOF is uncommon. However, the formation of key structural Th-N bonds in TSN-626 cap some of the square antiprismatic metal centers, a position usually occupied by terminal water ligands. TSN-626 was characterized by using complementary analytical and computational techniques: X-ray diffraction, vibrational spectroscopy, N 2 physisorption isotherms, and density functional theory. TSN-626 satisfies design aspects for the chemisorption of iodine. The synergy between accessibility through pores, vacancies at the metal-oxo nodes, and pendent N-donor sites allowed a saturated iodine loading of 955 mg g -1 by vapor methods. The crystallization of TSN-626 diversifies actinide-MOF linker selection to include soft electron donors, and these Th-N linkages can be leveraged for the investigation of metal-to-ligand bonding and unconventional topological expressions.

Among the solution-processed devices, perovskite solar cells (PSCs) exhibit the highest power conversion efficiency (PCE) of over 25%; tremendous efforts are being undertaken to improve their stability. Recently, all-inorganic CsPbI 2 Br-based PSCs were reported to exhibit a significantly improved device stability, with a promising PCE of up to 16.79%. In this study, we report stable all-inorganic PSCs by incorporating novel dopant-free hole-transporting materials (HTMs). The synthesis strategy of the newly synthesized polymeric HTMs was similar to that of 2,2',7,7'-tetrakis( N , N -di- p -methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), with the exception that they were designed to exhibit dopant-free characteristics. In particular, their polymeric backbone structure was significantly simpler than that of spiro-OMeTADs, and they were easily synthesized in two steps from commercially available chemicals, with an overall yield of ∼50%. The cost of synthesis at the laboratory scale was calculated to be at least 2.4 times cheaper than that of spiro-OMeTADs. The PCE of dopant-free HTM-based PSCs was 11.01%, which is 1.5 times higher than that of the dopant-free spiro-OMeTAD-based devices (7.52%) and comparable to that of the doped spiro-OMeTAD-based devices (12.22%). Notably, the stability of the device based on our dopant-free HTM to atmospheric oxygen and moisture as well as heat and light irradiation was superior to that of devices based on doped and dopant-free spiro-OMeTAD HTMs. On consideration of the synthesis cost, device efficiency, and device stability, our dopant-free HTM is highly promising for all-inorganic PSCs.

Polymer nanofiber-based porous structures ("breathable devices") have been developed for breathable epidermal electrodes, piezoelectric nanogenerators, temperature sensors, and strain sensors, but their applications are limited because increasing the porosity reduces device robustness. Herein, we report an approach to produce ultradurable, cost-effective breathable electronics using a hierarchical metal nanowire network and an optimized photonic sintering process. Photonic sintering significantly reduces the sheet resistance (16.25 to 6.32 Ω sq -1 ) and is 40% more effective than conventional thermal annealing (sheet resistance: 12.99 Ω sq -1 ). The mechanical durability of the sintered (648.9 Ω sq -1 ) sample is notably improved compared to that of the untreated (disconnected) and annealed (19.1 kΩ sq -1 ) samples after 10,000 deformation cycles at 40% tensile strain. The sintered sample exhibits ∼29 times less change in electrical performance compared to the thermally annealed sample. This approach will lead to the development of affordable and ultradurable commercial breathable electronics.

We present the active learning configuration interaction (ALCI) method for multiconfigurational calculations based on large active spaces. ALCI leverages the use of an active learning procedure to find important electronic configurations among the full configurational space generated within an active space. We tested it for the calculation of singlet-singlet excited states of acenes and pyrene using different machine learning algorithms. The ALCI method yields excitation energies within 0.2-0.3 eV from those obtained by traditional complete active-space configuration interaction (CASCI) calculations (affordable for active spaces up to 16 electrons in 16 orbitals) by including only a small fraction of the CASCI configuration space in the calculations. For larger active spaces (we tested up to 26 electrons in 26 orbitals), not affordable with traditional CI methods, ALCI captures the trends of experimental excitation energies. Overall, ALCI provides satisfactory approximations to large active-space wave functions with up to 10 orders of magnitude fewer determinants for the systems presented here. These ALCI wave functions are promising and affordable starting points for the subsequent second-order perturbation theory or pair-density functional theory calculations.

Controlling the microstructures in fibers, such as crystalline structures and microvoids, is a crucial challenge for the development of mechanically strong graphene fibers (GFs). To date, although GFs graphitized at high temperatures have exhibited high tensile strength, GFs still have limited the ultimate mechanical strength owing to the presence due to the structural defects, including the imperfect alignment of graphitic crystallites and the presence of microsized voids. In this study, we significantly enhanced the mechanical strength of GF by controlling microstructures of fibers. GF was hybridized by incorporating polyacrylonitrile (PAN) in the graphene oxide (GO) dope solution. In addition, we controlled the orientation of the inner structure by applying a tensile force at 800 °C. The results suggest that PAN can act as a binder for graphene sheets and can facilitate the rearrangement of the fiber's microstructure. PAN was directionally carbonized between graphene sheets due to the catalytic effect of graphene. The resulting hybrid GFs successfully displayed a high strength of 1.10 GPa without undergoing graphitization at extremely high temperatures. We believe that controlling the alignment of nanoassembled structure is an efficient strategy for achieving the inherent performance characteristics of graphene at the level of multidimensional structures including films and fibers.

We investigate the effects of interfacial oxidation on the perpendicular magnetic anisotropy, magnetic damping, and spin-orbit torques in heavy-metal (Pt)/ferromagnet (Co or NiFe)/capping (MgO/Ta, HfO x , or TaN) structures. At room temperature, the capping materials influence the effective surface magnetic anisotropy energy density, which is associated with the formation of interfacial magnetic oxides. The magnetic damping parameter of Co is considerably influenced by the capping material (especially MgO) while that of NiFe is not. This is possibly due to extra magnetic damping via spin-pumping process across the Co/CoO interface and incoherent magnon generation (spin fluctuation) developed in the antiferromagnetic CoO. It is also observed that both antidamping and field-like spin-orbit torque efficiencies vary with the capping material in the thickness ranges we examined. Our results reveal the crucial role of interfacial oxides on the perpendicular magnetic anisotropy, magnetic damping, and spin-orbit torques.

Self-assembly of two-dimensional MXene sheets is used in various fields to create multiscale structures due to their electrical, mechanical, and chemical properties. In principle, MXene nanosheets are assembled by molecular interactions, including hydrogen bonds, electrostatic interactions, and van der Waals forces. This study describes how MXene colloid nanosheets can form self-supporting MXene hydrogels. Three-dimensional network structures of MXene gels are strengthened by reinforced electrostatic interactions between nanosheets. Stable gel networks are beneficial for fabricating highly aligned fibers because MXene gel can endure structural deformation. During wet spinning of highly concentrated MXene colloids in a coagulation bath, MXene sheets can be transformed into perfectly aligned fibers under a mechanical drawing force. Oriented MXene fibers exhibit a 1.5-fold increase in electrical conductivity (12 504 S cm -1 ) and Young's modulus (122 GPa) compared with other fibers. The oriented MXene fibers are expected to have widespread applications, including electrical wiring and signal transmission.

Conformal integration of an epidermal device with the skin, as well as sweat and air permeability, are crucial to reduce stress on biological tissues. Nanofiber-based porous mesh structures (breathable devices) are commonly utilized to prevent skin problems. Noble metals are normally deposited on nanomesh substrates to form breathable electrodes. However, these are expensive and require high-vacuum processes involving time-consuming multistep procedures. Organic materials are suitable alternatives that can be simply processed in solution. We report a simple, cost-effective, mechanically biocompatible, and breathable organic epidermal electrode for biometric devices. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is sprayed on a nanofiber-mesh structure, treated using only heat and water to enhance its biocompatibility and conductivity, and used as the electrode. The treatment is accomplished using an autoclave, simultaneously reducing the electrical resistance and sterilizing the electrode for practical use. This research can lead to affordable and biocompatible epidermal electrodes with improved suitability for various biomedical applications.

Neural network potentials (NNPs) are gaining much attention as they enable fast molecular dynamics (MD) simulations for a wide range of systems while maintaining the accuracy of density functional theory calculations. Since NNP is constructed by machine learning on training data, its prediction uncertainty increases drastically as atomic environments deviate from training points. Therefore, it is essential to monitor the uncertainty level during MD simulations to judge the soundness of the results. In this work, we propose an uncertainty estimator based on the replica ensemble in which NNPs are trained over atomic energies of a reference NNP that drives MD simulations. The replica ensemble is trained quickly, and its standard deviation provides atomic-resolution uncertainties. We apply this method to a highly reactive silicidation process of Si(001) overlaid with Ni thin films and confirm that the replica ensemble can spatially and temporally trace simulation errors at atomic resolution, which in turn guides the augmentation of the training set. The refined NNP completes a 3.6 ns simulation without any noticeable problems. By suggesting an efficient and atomic-resolution uncertainty indicator, this work will contribute to achieving reliable MD simulations by NNPs.

Energy-efficient solution-processed organic field-effect transistors (OFETs) are highly sought after in the low-cost printing industry as well as for the manufacture of flexible and other next-generation devices. The fabrication of such electronic devices requires high-functioning insulating materials that are chemically and mechanically robust to avoid lowering insulating properties during the device fabrication process or utilization of devices. In this study, we report a facile, fluorinated, UV-assisted cross-linker series using a fluorophenyl azide (FPA), which reacts with the C-H groups of a conventional polymer. This demonstrates the application of the cross-linked films in OFET gate dielectrics. The effects of the cross-linkable chemical structure of the FPA series on the cross-linking chemistry, photopatternability, and dielectric properties of the resulting films are investigated for low/high- k or amorphous/crystalline polymeric gate dielectric materials. The characteristics of insulating layers and behavior of OFETs containing these cross-linked gate dielectrics (for example, leakage current density ( J ), hysteresis, and charge trap density) depend on the polymer type. Furthermore, an organic-based complementary inverter and various printable OFETs with excellent electrical characteristics are successfully fabricated. Thus, these reported cross-linkers that enable the solution process and patterning of well-developed conventional polymer dielectric materials are promising for the realization of a more sustainable next-generation industrial technology for flexible and printable devices.

We report the synthesis and characterization of the first plutonium metal-organic framework (MOF). Pu-UiO-66 expands the established UiO-66 series, which includes transition metal, lanthanide, and early actinide elements in the hexanuclear nodes. The thermal stability and porosity of Pu-UiO-66 were experimentally determined, and multifaceted computational methods were used to corroborate experimental values, examine inherent defects in the framework, decipher spectroscopic signatures, and elucidate the electronic structure. The crystallization of a plutonium chain side product provides direct evidence of the competition that occurs between modulator and linker in MOF syntheses. Ultimately, the synthesis of Pu-UiO-66 demonstrates adept control of Pu(IV) coordination under hydrolysis-prone conditions, provides an opportunity to extend trends across isostructural UiO-66 frameworks, and serves as the foundation for future plutonium MOF chemistry.

Predicting and understanding the chemical bond is one of the major challenges of computational quantum chemistry. Kohn-Sham density functional theory (KS-DFT) is the most common method, but approximate density functionals may not be able to describe systems where multiple electronic configurations are equally important. Multiconfigurational wave functions, on the other hand, can provide a detailed understanding of the electronic structures and chemical bonds of such systems. In the complete active space self-consistent field (CASSCF) method, one performs a full configuration interaction calculation in an active space consisting of active electrons and active orbitals. However, CASSCF and its variants require the selection of these active spaces. This choice is not black box; it requires significant experience and testing by the user, and thus active space methods are not considered particularly user-friendly and are employed only by a minority of quantum chemists. Our goal is to popularize these methods by making it easier to make good active space choices. We present a machine learning protocol that performs an automated selection of active spaces for chemical bond dissociation calculations of main group diatomic molecules. The protocol shows high prediction performance for a given target system as long as a properly correlated system is chosen for training. Good active spaces are correctly predicted with a considerably better success rate than random guess (larger than 80% precision for most systems studied). Our automated machine learning protocol shows that a "black-box" mode is possible for facilitating and accelerating the large-scale calculations on multireference systems where single-reference methods such as KS-DFT cannot be applied.

Z-scheme transfer is an ideal photocatalytic system with stronger redox ability, but its design and construction still lack understanding. Herein, the work function difference and the band bending are found to be the determining factors for the construction of the Z-scheme transfer mechanism of photoexcited charges in TiO 2 /WO 3 . The control of work function and band bending achieved by carbon insertion results from the hybridization of orbitals and redistribution of electron density, as demonstrated by ultraviolet photoelectron spectroscopy and photocatalytic analysis. The heterojunction system, TiO 2 /WO 3 , with controlled work function and band bending, shows 2 times faster • OH radical formation rate (0.011 μmol min -1 ) compared to the undisturbed system. First-principles calculation reveals that the changes in work function and band bending result in an interfacial electric field, which shifts the charge transfer mechanism from type II to Z-scheme. This work proves that the design of work function and band bending allows reconstructing charge transfer mechanism by forming the interfacial electric field in heterojunction systems.

The importance of monitoring the condition of skin is increasing as its relevance to health is becoming more well understood. Inappropriate humidity levels can cause atopic dermatitis or hair loss. However, conventional film substrates used in electronic skin monitoring devices cause accumulation of sweat or gas between the device and biological tissue, leading to negative effects in long-term humidity measurements. Thus, real-time measurements of skin humidity over long periods are difficult using conventional film devices. Here, a breathable nanomesh humidity sensor that can monitor skin humidity for a long time is developed by using biocompatible materials such as gold, poly(vinyl alcohol), and Parylene C. The sensor presents excellent gas and sweat permeability and precisely detects the humidity level of an object for a long time. This study demonstrates the successful real-time detection of the humidity level from human skin and also detects the relative humidity of a plant surface over a prolonged period. This sensor is expected to have wide applicability for cultivating delicate plants as well as to reveal correlations between skin humidity and disease for biomedical applications.

In this study, we developed a uniform initiator layer that can be formed on various surfaces, and formed site-selectively, for the subsequent antifouling polymer brush formation. Initially, metal-organic films composed of tannic acid (TA) and Fe III ions (TA-Fe III ) were formed on various surfaces, followed by functionalization with an aryl azide-based initiator (ABI) under photoreaction. In particular, combination with a photolithographic technique enabled the presentation of initiators only on the intended region within a single-surface platform. A resultant initiator film (TF-ABI) was formed under mild reaction conditions and meets the uniformity and transparency requirements concurrently. Subsequently, we showed that TF-ABI can be further utilized to form a polymer brush by proceeding with surface-initiated polymerization using a zwitterionic monomer, namely, sulfobetaine acrylamide (SBAA). Instead of applying a classical, yet air-sensitive atom transfer radical polymerization (ATRP) technique, we utilized an activator regenerated by electron transfer (ARGET) ATRP under air conditions without a cumbersome deoxygenation step. Overall, our initiator layer allowed the antifouling poly(SBAA) brush to be used on various surfaces, and enabled their pattern generation.

In nature, many cells possess cilia that provide them with motor or sensory functions, allowing organisms to adapt to their environment. The development of artificial cilia with identical or similar sensory functions will enable high-performance and flexible sensing. Here, we investigate a method of producing artificial cilia composed of various polymer materials, such as polyethylene terephthalate, polyurethane, poly(methyl methacrylate), polyvinylpyrrolidone, polystyrene, polyvinyl chloride, and poly (allylamine hydrochloride), using a field effect spinning (FES) method. Unlike wet- or electro-spinning, in which single or multiple strands of fibers are pulled without direction, the FES method can grow fiber arrays vertically and uniformly on a substrate in cilia-like patterns. The lengths and diameters of the vertically grown artificial cilia can be controlled by the precursor polymer concentration in the solution, applied electric current and voltage, and shape and size of the needle tip used for FES. The red, green, and blue emission characteristics of the polymer-quantum dot-based self-emitting artificial cilia prepared in polymer-inorganic nanoparticle hybrid form were determined. In addition, an artificial cilia-based humidity sensor made of the polymer-polymer composite was fabricated.

The formation of a dense zwitterionic brush through surface-initiated atom transfer radical polymerization (SI-ATRP) is a typical graft-from approach used to achieve antifouling surfaces with high fidelity; however, their air-tightness may cause inconvenience to users. In this context, activator regenerated by electron transfer (ARGET) ATRP is emerging as an alternative surface-coating tool because limited amount of air is allowed to form a dense polymer brush. However, the degree of air tolerance that can ensure a thick polymer brush has not been clearly defined, limiting its practical usage under ambient-air conditions. In this study, we investigated the SI-ARGET ATRP of carboxybetaine (CB) by changing the air conditions, along with the air-related parameters, such as the concentration of the reducing agent, the volume of the polymerization solution (PS), or the solvent composition, and correlated their effects with the poly(CB) thickness. Based on the optimized reaction conditions, a poly(CB) brush with reliable thickness was feasibly formed even under open-air conditions without a degassing step. In addition, a microliter droplet (∼100 μL) of PS was sufficient to proceed with the SI-ARGET ATRP for the covering of a poly(CB) brush on the surface area of interest. By applying an optimized SI-ARGET ATRP of CB, antifouling was feasibly achieved in the surface region of interest using an array to form a large surface area under fully exposed air conditions. In other words, optimized SI-ARGET ATRP enabled the formation of a thick poly(CB) brush on the surfaces of various dimensions under open-air conditions.

A new palladium-catalyzed asymmetric addition reaction of indoles to alkoxyallenes is reported. Remarkably, the reaction showed complete regioselectivity toward the nitrogen. A new mechanism distinct from that of conventional π-allyl chemistry is proposed to explain this unique selectivity. The utility of the reaction is demonstrated by highly efficient and flexible synthesis of N-glycosylindoles.

Owing to a unique colorimetric (typically blue-to-red) feature upon environmental stimulation, polydiacetylenes (PDAs) have been actively employed in chemosensor systems. We developed a highly accurate and simple volatile organic compound (VOC) sensor system that can be operated using a conventional smartphone. The procedure begins with forming an array of four different PDAs on conventional paper using inkjet printing of four corresponding diacetylenes followed by photopolymerization. A database of color changes (i.e., red and hue values) is then constructed on the basis of different solvatochromic responses of the 4 PDAs to 11 organic solvents. Exposure of the PDA array to an unknown solvent promotes color changes, which are imaged using a smartphone camera and analyzed using the app. A comparison of the color changes to the database promoted by the 11 solvents enables the smartphone app to identify the unknown solvent with 100% accuracy. Additionally, it was demonstrated that the PDA array sensor was sufficiently sensitive to accurately detect the 11 VOC gases.

Catalytic asymmetric synthesis of N-heterocyclic glycosides free of protecting and directing groups is reported. The key reaction is highlighted by the atom-efficient and regioselective addition of unprotected pyrimidines to highly functionalized alkoxyallene. Numerous acyclic and cyclic N-heterocyclic glycosides are accessed with minimal formation of organic byproducts. The synthetic utility of the reaction is demonstrated by the first catalytic asymmetric synthesis of anticancer pharmaceutical (-)-Tegafur and stereoselective synthesis of an oxepane nucleoside derivative.

A flexible synthetic method toward highly substituted tetrahydropyran is reported. The key transformation involves atom-efficient sequential metal catalysis consisting of Pd-catalyzed addition of homopropargylic alcohols to alkoxyallene and the subsequent gold(I)-catalyzed cycloisomerization. Notably, this method gives access to both 2,6-cis- and 2,6-trans-tetrahydropyrans possessing diverse substitution patterns.

Understanding energy dissipation at the nanoscale requires the ability to probe temperature fields with nanometer resolution. Here, we describe an ultra-high vacuum (UHV)-based scanning thermal microscope (SThM) technique that is capable of quantitatively mapping temperature fields with ∼15 mK temperature resolution and ∼10 nm spatial resolution. In this technique, a custom fabricated atomic force microscope (AFM) cantilever, with a nanoscale Au-Cr thermocouple integrated into the tip of the probe, is used to measure temperature fields of surfaces. Operation in an UHV environment eliminates parasitic heat transport between the tip and the sample enabling quantitative measurement of temperature fields on metal and dielectric surfaces with nanoscale resolution. We demonstrate the capabilities of this technique by directly imaging thermal fields in the vicinity of a 200 nm wide, self-heated, Pt line. Our measurements are in excellent agreement with computational results-unambiguously demonstrating the quantitative capabilities of the technique. UHV-SThM techniques will play an important role in the study of energy dissipation in nanometer-sized electronic and photonic devices and the study of phonon and electron transport at the nanoscale.

A new gold(I)-catalyzed cycloisomerization to access highly substituted piperidines has been developed. By combining a conceptually new way of generating iminium ions using cationic gold(I) complexes and an efficient cyclization reaction that can minimize a potentially competing aza-Cope rearrangement, the proposed reaction successfully circumvents a long-standing problem in the classical aza-Prins reaction. Synthetic utility of the catalytic reaction was demonstrated by a synthesis of optically active 2-alkyl-piperidin-4-one.

The zwitterionic ring-opening polymerization of lactide initiated by N-heterocyclic carbenes generates cyclic polylactides with well-defined molecular weights between M(n) = 5000 and 30,000 g/mol with narrow polydispersities (M(w)/M(n) < or = 1.31). These zwitterionic polymerizations are extremely rapid (k(p) = 48.7 M(-1) s(-1)), but also exhibit exceptional control of molecular weight and molecular weight distribution. The unusual kinetic features of these zwitterionic polymerizations are illuminated with kinetic and mechanistic investigations, which implicate a mechanism that involves a slow initiation step (second order in [M]), a propagation step (first order in [M]) that is much faster than initiation (k(i) = 0.274 M(-2) s(-1)), cyclization (k(c) = 0.0575 s(-1)), and depropagation (k(d) = 0.208 s(-1)). Numerical and stochastic simulations of the kinetic data provide a kinetic rationale for the evolution of molecular weight with monomer conversion: the molecular weights increase with increasing monomer conversion, exhibit a nonzero intercept near 0% monomer conversion, and are relatively insensitive to the initial monomer-to-initiator ratio. The observed narrow molecular weight distributions are due to a high rate of propagation relative to cyclization and chain transfer. Kinetic simulations define the kinetic criteria under which the active zwitterions remain in solution; these simulations were substantiated by chain-extension experiments, which provide experimental evidence for chain extension of the zwitterions and reinitiation by the N-heterocyclic carbenes liberated upon macrocyclization. The kinetic model rationalizes some of the unique features of zwitterionic ring-opening polymerization and provides a useful mechanistic framework to optimize these polymerizations as a strategy to generate well-defined cyclic polyesters.

The catalytic cysteine of certain members of the peroxiredoxin (Prx) family can be hyperoxidized to cysteinesulfinic acid during reduction of peroxides. Sulfiredoxin is responsible for the ATP-dependent reduction of cysteinesulfinic acid (SO2H) of hyperoxidized Prx. Here we report the NMR solution structure of human sulfiredoxin (hSrx), both with and without bound ATP, and we model the complex of ATP-bound hSrx with Prx. Binding ATP causes only small changes in the NMR structure of hSrx, and the bound ATP conformation is quite similar to that seen for the previously reported X-ray structure of the ADP-hSrx complex. Although hSrx binds ATP, it does not catalyze hydrolysis by itself and has no catalytic acid residue typical of most ATPase and kinase family proteins. For modeling the complex, the ATP-bound hSrx was docked to hyperoxidized Prx II using EMAP of CHARMM. In the model complex, Asn186 of Prx II (Asp187 of Prx I) is in contact with the hSrx-bound ATP beta- and gamma-phosphate groups. Asp187 of Prx I was mutated to alanine and asparagine, and binding and activity of the mutants with hSrx were compared to those of the wild type. For the D187N mutant, both binding and hydrolysis and reduction activities were comparable to those of the wild type, whereas for D187A, binding was unimpaired but ATP hydrolysis and reduction did not occur. The modeling and mutagenesis analyses strongly implicate Asp187 of Prx I as the catalytic residue responsible for ATP hydrolysis in the cysteinesulfinic acid reduction of Prx by hSrx.

We previously reported on a rheological study of Langmuir films of poly(tert-butyl methacrylate) (PtBMA), and this work describes further studies on this system. Here, surface pressure-area (Pi-A) isotherms and interfacial shear rheology experiments are performed to better understand the effects of two modifications: varying the temperature between 5 and 40 degrees C and introducing small amounts of carboxylic acid groups by partially hydrolyzing the polymer. Increased temperature produced isotherms with lower plateau surface pressures, Pip, and Pi values shifted to lower areas above Pip. Film properties transition from being primarily viscous to being dominated by elasticity as Pip is crossed for all temperatures studied, even as the value of Pip changes. Increasing the hydrolysis fraction leads to isotherms shifted to lower areas throughout the curve and higher Pip values. Both temperature variation and chemical modification are believed to affect the relative importance of polymer-polymer and polymer-subphase interactions.