Tunable Strategy Research Articles

Synergistic Dual Role of [hmim]Br-ArSO2Cl in Cascade Sulfenylation-Halogenation of Indole: Mechanistic Insight into Regioselective C-S and C-S/C-X (X = Cl and Br) Bond Formation in One Pot.

Bifunctionalized indoles are an important class of biologically active heterocyclic compounds and potential drug candidates. Because of the lack of efficient synthetic methods, one pot cascade synthesis of these compounds is rare and remains a challenge. To expand this field, we herein disclose a step-economical and temperature tunable strategy wherein the synergistic effect between [hmim]Br-ArSO2Cl leads exclusively to the formation of 3-arylthio indole via sulfenylation of indole at room temperature, while heating the reaction mixture at 50 °C provided an unexpected 2-halo-3-arylthio indole with construction of C-S and C-S/C-X (X = Cl and Br) bonds without addition of any external halogenating agent via cascade sulfenylation-halogenation reactions under metal-oxidant-base-free conditions. Further, insight into the reaction mechanism provides an unprecedented observation wherein the synergistic interaction between [hmim]Br-ArSO2X in the presence of a catalytic amount of water generates arylsulfonic anhydride (ArSO2)2O in situ as a new sulfur source along with the formation of [hmim]PTS as probed by NMR, ESI-MS, DART-MS, and HPLC studies. Notably, the mixture of bifunctionalized 2-halo(Br/Cl)-3-arylthio indole was smoothly diversified with privileged heterocycle triazole to provide 2-(1 H-triazole-1-yl)-3-arylthio indole, which is an analogue of the potent indole-based anticancer agent.

Aptamer-based colorimetric detection of various targets based on catalytic Au NPs/Graphene nanohybrids

In this paper, a label-free aptamer-based colorimetric assay was developed by incorporating catalytic Au nanoparticles/Graphene (Au NPs/Gr) nanohybrids. As an efficient peroxidase mimic, Au NPs/Gr can oxidize ABTS112,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) in the presence of H2O2, generating visible color change that can be recorded by a simple UV–vis spectrophotometer. The ssDNA aptamer can absorb on Au NPs/Gr interface through non-covalent interaction, thereby reducing the catalytic activity of Au NPs/Gr. In the presence of target molecule, the combination of aptamer with target caused the aptamer to assume a folded state and lose its ability to bind with Au NPs/Gr, leading to recovery of the catalytic activity of Au NPs/Gr. Base on this tunable strategy, calibration curves obtained for Hg2+ and MC-LR have detection limits of 3.63 nM and 7.14 ng/L with the linear range of 0.01–0.5 μM and 0.01–1.0 μg/L, respectively. These results indicated that various targets could be detected by this simple, rapid and universal colorimetric assay based on catalytic nanomaterials.

Magic spot nucleotides: tunable target-specific chemoenzymatic synthesis.

A tunable chemoenzymatic strategy provides access to the entire class of magic spot nucleotides and modified analogues. The approach combines chemoselective bisphosphorylations using phosphoramidites with regioselective ribonuclease T2 cyclo-phosphate hydrolysis, leading to flexible and simple gram-scale operations.

High hardness dual-phase high entropy alloy thin films produced by interface alloying

In this work, we present a tunable alloying strategy to prepare high entropy alloy (HEA) thin films with FCC/BCC dual-phase structure. The dual-phase HEA films consist of uniformly equiaxed grains with average size about 40 nm. Comparing with single-phase FCC HEA, the dual-phase HEA has higher hardness up to 10.4 GPa. The relative large atomic radius of Al leads to severe lattice distortion, resulting in a stronger solid solution strengthening behavior in the dual-phase HEA. Moreover, high dense heterogeneous phase interfaces effectively blocking dislocation motion enhance the strain hardening ability further.

Synthesis, Characterization, and Electromagnetic Wave Absorption Properties of Composites of Reduced Graphene Oxide with Porous LiFe5O8 Microspheres

A novel three-dimensional composite of reduced graphene oxide sheets and porous LiFe5O8 microspheres was fabricated via a facile, green, and highly tunable strategy, and the microstructure, composition, and microwave-absorbing performances of the rGO/porous LiFe5O8 composite were characterized and investigated. The experimental results indicate that the porous LiFe5O8 microspheres are dispersed on the thin rGO sheets uniformly. Compared with the pure LiFe5O8 particles and porous LiFe5O8 microspheres, the as-prepared rGO/porous LiFe5O8 composites exhibit outstanding microwave-absorbing performances including efficient bandwidth and reflection loss. The rGO/porous LiFe5O8 composite (S-50) displays a maximum reflection loss of −53.4 dB at 12.2 GHz with a coating layer thickness of 2.2 mm and a broad effective bandwidth of 3.5 GHz (from 10.4 to 13.9 GHz). The outstanding microwave-absorbing performances are assigned to employing magnetic microflowers with multi-interfaces to improve impedance matching, which ...

Mixed cation perovskite solar cells by stack-sequence chemical vapor deposition with self-passivation and gradient absorption layer

Mixed cation halide perovskite solar cells (PSCs), in a formula of ABX3 where A is a mixture of formamidinium (FA) or cesium (Cs) cations, represent a promising new architecture to achieve largely improved stability and higher power conversion efficiency (PCE). While all these mixed-cation PSCs were synthesized via a solution method, we here propose and demonstrate a precisely tunable stack sequence physical-chemical vapor deposition (SS-PCVD) approach to prepare a mixed-cation absorber in CsBr-doped hybrid organic perovskite, which features a beneficial gradient bandgap profile to enable an improvement of PCE from 11.69% in pure FAPbI3 to 18.22% in mixed-cation PSCs. Remarkably, an excellent stability in ambient exposure for 60 days has been achieved by a proper control of the CsBr cation incorporation and interface passivation. This new approach indicates a simple, precisely tunable and low cost fabrication strategy to implement high performance and scalable mixed-cation halide perovskite solar cells.

Tunable Confinement for Bridging Single-Cell Manipulation and Single-Molecule DNA Linearization.

DNA linearization by nanoconfinement has offered a new avenue toward large-scale genome mapping. The ability to smoothly interface the widely different length scales from cell manipulation to DNA linearization is critical to the development of single-cell genomic mapping or sequencing technologies. Conventional nanochannel technologies for DNA analysis suffer from complex fabrication procedures, DNA stacking at the nanochannel entrance, and inefficient solution exchange. In this work, a dynamic and tunable confinement strategy is developed to manipulate and linearize genomic-length DNA molecules from a single cell. By leveraging pneumatic microvalve control and elastomeric collapse, an array of nanochannels with confining dimension down to 20 nm and length up to sub-millimeter is created and can be dynamically tuned in size. The curved edges of the microvalve form gradual transitions from microscale to nanoscale confinement, smoothly facilitating DNA entry into the nanochannels. A unified micro/nanofluidic device that integrates single-cell trapping and lysis, DNA extraction, purification, labeling, and linearization is developed based on dynamically controllable nanochannels. Mbp-long DNA molecules are extracted directly from a single cell and in situ linearized in the nanochannels. The device provides a facile and promising platform to achieve the ultimate goal of single-cell, single-genome analysis.

A “fullerene-carbon nanotube” structure with tunable mechanical properties

Carbon-based nanostructures have drawn tremendous research interest and become promising building blocks for the new generation of smart sensors and devices. Utilizing a bottom-up strategy, the chemical interconnecting sp3 covalent bond between carbon building blocks is an efficient way to enhance its Young's modulus and ductility. The formation of sp3 covalent bond, however, inevitably degrades its ultimate tensile strength caused by stress concentration at the junction. By performing a molecular dynamics simulation of tensile deformation for a fullerene-carbon nanotube (FCNT) structure, we propose a tunable strategy in which fullerenes with various angle energy absorption capacities are utilized as building blocks to tune their ductile behavior, while still maintaining a good ultimate tensile strength of the carbon building blocks. A higher ultimate tensile strength is revealed with the reduction of stress concentration at the junction. A brittle-to-ductile transition during the tensile deformation is detected through the structural modification. The development of ductile behavior is attributed to the improvement of energy propagation ability during the fracture initiation, in which the released energy from bonds fracture is mitigated properly, leading to the further development of mechanical properties.

A Tunable Route to Prepare α,β‐Unsaturated Esters and α,β‐Unsaturated‐γ‐Keto Esters through Copper‐Catalyzed Coupling of Alkenyl Boronic Acids with Phosphorus Ylides

AbstractA tunable strategy to prepare α,β‐unsaturated esters and α,β‐unsaturated‐γ‐keto esters in good to excellent yields was developed through copper‐catalyzed oxidative coupling of phosphorus ylides with alkenyl boronic acids under mild conditions. The reaction without water afforded α,β‐unsaturated esters, ketones, and amides while α,β‐unsaturated‐γ‐keto esters, 1,4‐α,β‐unsaturated diketones and α,β‐unsaturated‐γ‐keto amides were obtained when using 5.0 equiv. of water. H2O18 labeling experiments showed that water played an important role in the formation of α,β‐unsaturated‐γ‐keto esters. A plausible formation mechanism for α,β‐unsaturated esters and α,β‐unsaturated‐γ‐keto esters was proposed based on mechanistic studies. Phosphonium salts could also be used directly as coupling partners instead of phosphorus ylides. The reaction exhibited a broad substrate scope, good functional group tolerance, good regioselectivity, and diverse coupling products.magnified image

A facile fabrication and highly tunable microwave absorption of 3D flower-like Co3O4-rGO hybrid-architectures

Electromagnetic absorption materials have drawn increasing attention owing to their wide applications in military, aerospace, communication and the electronic industry. Efficient microwave absorption with tunable bandwidth and thermal stability is a great challenge. Herein, we fabricate a novel 3D hierarchical Co3O4-rGO hybrid-architecture by a facile, green and highly tunable strategy. The porous Co3O4 flower is assembled uniformly, introducing great amount of interfaces. Tailoring Co3O4 flowers could improve interfacial polarization and dipole polarization as well as conductive network, highly tuning the hybrid-architectures and electromagnetic properties. The reflection loss (RL) reaches −61 dB at Co3O4/rGO ratio of 2:1, as well as frequency-selective absorption. Furthermore, the RL are relatively stable and the bandwidth is broadened almost covering the whole investigated frequency at elevated temperature of 353–473 K. The result is ascribed to utilizing multi-interface magnetic micro-flowers to tune impedance matching, which is accompanied with strong relaxation loss and electrical loss, as well as magnetic loss. Our work confirms that 3D hierarchical Co3O4-rGO hybrids as a potential candidate for high-efficiency microwave absorbers in harsh environment, and provide a novel pathway for designing microwave absorber in the future.

An update on coating/manufacturing techniques of microneedles.

Recently, results have been published for the first successful phase I human clinical trial investigating the use of dissolving polymeric microneedles… Even so, further clinical development represents an important hurdle that remains in the translation of microneedle technology to approved products. Specifically, the potential for accumulation of polymer within the skin upon repeated application of dissolving and coated microneedles, combined with a lack of safety data in humans, predicates a need for further clinical investigation. Polymers are an important consideration for microneedle technology-from both manufacturing and drug delivery perspectives. The use of polymers enables a tunable delivery strategy, but the scalability of conventional manufacturing techniques could arguably benefit from further optimization. Micromolding has been suggested in the literature as a commercially viable means to mass production of both dissolving and swellable microneedles. However, the reliance on master molds, which are commonly manufactured using resource intensive microelectronics industry-derived processes, imparts notable material and design limitations. Further, the inherently multi-step filling and handling processes associated with micromolding are typically batch processes, which can be challenging to scale up. Similarly, conventional microneedle coating processes often follow step-wise batch processing. Recent developments in microneedle coating and manufacturing techniques are highlighted, including micromilling, atomized spraying, inkjet printing, drawing lithography, droplet-born air blowing, electro-drawing, continuous liquid interface production, 3D printing, and polyelectrolyte multilayer coating. This review provides an analysis of papers reporting on potentially scalable production techniques for the coating and manufacturing of microneedles.

Combination of Magnetic Lignocellulosic Particles, High-Density Polyethylene, and Carbon Black for the Construction of Composites with Tunable Functionalities.

Biocomposites with unique functionalities for tailored applications are promising products for a sustainable future. In this work, a process concept of forming functional composites by combining of high-density polyethylene, carbon black, and magnetic lignocellulosic particles (wood flour) was demonstrated. The impacts of process parameters on morphologies, crystalline phase, and magnetic intensity of wood flour were identified. Magnetic, antistatic and mechanical properties of biocomposites were also evaluated. Lignocellulosic particles were encapsulated with magnetic nanoparticles, and the resulting composites exhibited tunable magnetic and antistatic properties. A noticeable feature is that magnetic nanoparticles were uniformly distributed in the matrices as a result of anchorage to lignocellulosic particles. Magnetic lignocellulosic particles and polymer resin had good compatibility. The resulting composites provided another opportunity for shielding materials, which could reduce the radiation in the living environment. These findings could provide a tunable strategy of the tailored use of lignocellulose-based composites in functional applications.

The mediated synthesis of FeF3 nanocrystals through (NH4)3FeF6 precursors as the cathode material for high power lithium ion batteries

The exploration of cathode materials with high electrochemical performances is critical to improve the energy and power densities of lithium ion batteries (LIBs). Iron fluoride (FeF3) has been proposed as an ideal candidate of LIBs cathode material because of the high discharge plateau and theoretical capacity. In this study, a precursor-mediated method was proposed to synthesize FeF3 nanocrystals (NCs) with different microstructures. These FeF3 NCs were obtained through the thermal decomposition of the precipitated ammonium hexafluoroferrate [(NH4)3FeF6] precursor, and the morphology and crystallinity could be adjusted by varying the ethanol/water volume ratio in the procursor precipitation process. Electrochemical studies demonstrated that FeF3 NC, derived from (NH4)3FeF6 precipitated from the solution with the ethanol/water volume ratio of 20, delivered the initial specific capacity of 217.6mAhg−1 at 0.2C, associated with excellent rate capability up to 20C (93.8mAhg−1), and showed the capacity retention of 80.6% after 500 cycles at 20C. These results indicate a tunable and convenient strategy towards nanostructured metals fluorides for high power LIBs.

Combinatorial Evolution of Fast-Conducting Highly Selective K+-Channels via Modularly Tunable Directional Assembly of Crown Ethers.

We describe here a modularly tunable molecular strategy for construction and combinatorial optimization of highly efficient K+-selective channels. In our strategy, a highly robust supramolecular H-bonded 1D ensemble was used to order the appended crown ethers in such a way that they roughly stack on top of each other to form a channel for facilitated ion transport across the membrane. Among 15 channels that all prefer K+ over Na+ ions, channel molecule 5F8 shows the most pronounced optimum for K+ while disfavoring all other biologically important cations (e.g., Na+, Ca2+ and Mg2+). With a K+/Na+ selectivity of 9.8 and an EC50 value of 6.2 μM for K+ ion, 5F8 is clearly among the best synthetic potassium channels developed over the past decades.

Phytosterol-based oleogels self-assembled with monoglyceride for controlled volatile release.

Oleogels have recently emerged as a subject of growing interest among industrial and academic researchers as an alternative to saturated/trans-fat and delivery of functional ingredients. Phytosterols, comprising plant-derived natural steroid compounds, are preferred for oleogel production because they are both natural and healthy. In the present study, phytosterol-based oleogels self-assembled with monoglyceride were studied with respect to tuning volatile release. Microscopy images of the bicomponent oleogels of β-sitosterol and monoglyceride showed the formation of a new three-dimensional network of entangled crystals and a controllable microstructure. Our analysis from differential scanning calorimetry and small angle X-ray scattering results suggests the self-assembly of β-sitosterol and monoglyceride via intermolecular hydrogen bonds into spherulitic microstructures. The results showed that the release rate (v0 ), maximum headspace concentrations (Cmax ) and partition coefficients (ka/o ) for oleogels showed a significantly controlled release and were tunable via the microstructure of phytosterol-based oleogels under both dynamic and static conditions. In addition, the solid-like oleogels had interesting thixotropic and thermoresponsive behaviors, probably as a result of intermolecular hydrogen bonding. The self-assembly of phytosterol-based oleogels with monoglyceride was attributed to intermolecular hydrogen and is demonstrated to be a promising tunable and functional strategy for delivering flavor compounds. © 2017 Society of Chemical Industry.

Graphene Oxide-Directed Tunable Assembly of MoS2 Ultrathin Nanosheets for Electrocatalytic Hydrogen Evolution

Three dimensional (3D) hierarchical architectures based on molybdenum disulfide (MoS2) and reduced graphene oxide (rGO) are synthesized through a mixed solvothermal method. By simply increasing the amount of graphene oxide (GO) during the synthesis, the 3D assembly of MoS2 can be tuned from nanoflowers to cross-linked nanosheets firmly attached to rGO. The structural and compositional analysis show that MoS2 nanostructures in the hybrids are constituted by ultrathin nanosheets with single or a few layers, and the GO precursor is reduced as rGO simultaneously. Due to the synergetic effects of rGO nanosheets and controllable assembly in MoS2 ultrathin nanostructures, the resulting nanohybrids show optimized electrocatalytic hydrogen evolution properties in 0.5 M H2SO4 solution. This work provides a facile method to increase the efficiency of hydrogen production for MoS2 based materials and their analogues via a tunable bottom-up assembly strategy.

Binder-free Ti3C2Tx MXene electrode film for supercapacitor produced by electrophoretic deposition method

Binder-free electrodes employed in supercapacitor devices can exhibit excellent electrochemical performances due to the improvement of electronic conductivity and the utilization rate of electrode materials. However, a simple, efficient and tunable strategy for preparation of binder-free MXene-based electrodes, especially for developing a general method for fabricating the MXene-based wearable flexible supercapacitors, still remains a challenge to meet the requirements of practical applications. In this study, we fabricated binder-free MXene-based films with adjustable mass loading and reduced agglomeration on the nickel foam and wearable flexible fabric substrates by the modified electrophoretic deposition method using organic colloid containing few-layers Ti3C2Tx nanoflakes. Their electrochemical performances are studied by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy, respectively. The binder-free electrodes can deliver high capacitance (∼140Fg−1 in alkaline electrolyte), stable cycling performance with no capacitance loss after 10,000 cycles and good rate performance, which can be attributed to the reduced agglomeration of Ti3C2Tx films with a layer-by-layer self-assembled stackable structure, optimized pore-size distribution (∼4nm) and excellent electronic conductivity, enhancing the accessibility to electrolyte ions and enabling full utilization of the MXene nanoflake surfaces.

Towards adaptable and tunable cloud-based map-matching strategy for GPS trajectories

Smart cities have given a significant impetus to manage traffic and use transport networks in an intelligent way. For the above reason, intelligent transportation systems (ITSs) and location-based services (LBSs) have become an interesting research area over the last years. Due to the rapid increase of data volume within the transportation domain, cloud environment is of paramount importance for storing, accessing, handling, and processing such huge amounts of data. A large part of data within the transportation domain is produced in the form of Global Positioning System (GPS) data. Such a kind of data is usually infrequent and noisy and achieving the quality of real-time transport applications based on GPS is a difficult task. The map-matching process, which is responsible for the accurate alignment of observed GPS positions onto a road network, plays a pivotal role in many ITS applications. Regarding accuracy, the performance of a map-matching strategy is based on the shortest path between two consecutive observed GPS positions. On the other extreme, processing shortest path queries (SPQs) incurs high computational cost. Current map-matching techniques are approached with a fixed number of parameters, i.e., the number of candidate points (NCP) and error circle radius (ECR), which may lead to uncertainty when identifying road segments and either low-accurate results or a large number of SPQs. Moreover, due to the sampling error, GPS data with a high-sampling period (i.e., less than 10 s) typically contains extraneous datum, which also incurs an extra number of SPQs. Due to the high computation cost incurred by SPQs, current map-matching strategies are not suitable for real-time processing. In this paper, we propose real-time map-matching (called RT-MM), which is a fully adaptive map-matching strategy based on cloud to address the key challenge of SPQs in a map-matching process for real-time GPS trajectories. The evaluation of our approach against state-of-the-art approaches is performed through simulations based on both synthetic and real-world datasets.

Assembly of Terpenoid Cores by a Simple, Tunable Strategy.

Oxygenated, polycyclic terpenoid natural products have important biological activities. Although total synthesis of such terpenes is widely studied, synthetic strategies that allow for controlled placement of oxygen atoms and other functionality remains a challenge. Herein, we present a simple, scalable, and tunable synthetic strategy to assemble terpenoid-like polycycloalkanes from cycloalkanones, malononitrile, and allylic electrophiles, abundantly available reagent classes.

Assembly of Terpenoid Cores by a Simple, Tunable Strategy

AbstractOxygenated, polycyclic terpenoid natural products have important biological activities. Although total synthesis of such terpenes is widely studied, synthetic strategies that allow for controlled placement of oxygen atoms and other functionality remains a challenge. Herein, we present a simple, scalable, and tunable synthetic strategy to assemble terpenoid‐like polycycloalkanes from cycloalkanones, malononitrile, and allylic electrophiles, abundantly available reagent classes.