Conspectus The widespread presence of hydrocarbons makes C–H functionalization an attractive alternative to traditional cross-coupling methods. As indole is an important heteroarene in a plethora of ...natural products and pharmaceuticals, C–H functionalization of indole moieties has emerged as one of the most important topics in this field. Due to the presence of multiple C–H bonds in indoles, site selectivity is a long-standing challenge. Much effort has been devoted to the C–H functionalization of indoles at the C3 or C2 position, while accessing the benzene core (from C4 to C7) is considerably more challenging. This Account summarizes our recent efforts toward site-selective C–H functionalization of indoles at the benzene core based on innovative strategies. A common method to solve the issue involves the development of directing groups (DGs). Our early studies establish that the installation of the N-P(O) t Bu2 group at the N position can produce C7 and C6 arylation products using palladium and copper catalysts, respectively. The developed system can also be extended to direct arylation of indoles at the C5 and C4 positions by installing a pivaloyl group at the C3 position. Further investigation of indoles bearing N-P t Bu2 groups shows a more diverse reactivity for C–H functionalizations at the C7 position, including arylation, olefination, acylation, alkylation, silylation, and carbonylation with different coupling partners. Compared to the P(V) DG, the P(III) group can be easily attached to the indole substrates and detached from the products. However, these attractive reactions rely mostly on precious metal catalysts with ligands; this requirement can be a significant limitation, particularly for large-scale syntheses and the necessity of removal of toxic trace metals in pharmaceutical products. We have also uncovered a general strategy for chelation-assisted aromatic C–H borylation just using simple BBr3 under mild conditions, in which the installation of pivaloyl groups at the N1 or C3 position of indoles can selectively deliver the boron species to the unfavorable C7 or C4 positions and allow subsequent C–H borylation without any metal. This transition-metal-free strategy can be extended to synthesize C7 and C4 hydroxylated indoles by boron-mediated directed C–H hydroxylation under mild reaction conditions and with broad functional group compatibility. In this Account, we describe our contributions to this topic since 2015. These studies provide efficient and attractive methods for the divergent synthesis of valuable substituted indoles and insights into the exploration of new strategies for the site-selective C–H functionalization and directives for other important heteroarenes.
Drug delivery systems (DDS) based on functionalized polymeric nanoparticles have attracted considerable attention. Although great advances have been reported in the past decades, the fabrication ...efficiency and reproducibility of polymeric nanoparticles are barely satisfactory due to the intrinsic limitations of the traditional self‐assembly method, which severely prevent further applications of the intelligent DDS. In the last decade, a new self‐assembly method, which is usually called polymerization‐induced self‐assembly (PISA), has become a powerful strategy for the fabrication of the polymeric nanoparticles with bespoke morphology. The PISA strategy efficiently simplifies the fabrication of polymeric nanoparticles (combination of the polymerization and self‐assembly in one pot) and allows the fabrication of polymeric nanoparticles at a relatively high concentration (up to 50 wt%), making it realistic for large‐scale production of polymeric nanoparticles. In this review, the developments of PISA‐based polymeric nanoparticles for drug delivery are discussed.
Drug delivery systems based on functionalized polymeric nanoparticles have attracted considerable attention. For fabrication of polymeric nanoparticles, polymerization‐induced self‐assembly (PISA) offers decisive advantages over conventional protocols in terms of efficiency and cost‐effectiveness. Recently, the nascent investigation of functional PISA‐generated nanocarriers with stimulus‐responsive drug release has already found applications in the biomedical area, which is discussed in this review.
Two‐dimensional/two‐dimensional (2D/2D) stacking heterostructures are highly desirable in fabricating efficient photocatalysts because face‐to‐face contact can provide a maximized interfacial region ...between the two semiconductors; this largely facilitates the migration of charge carriers. Herein, a WS2/graphitic carbon nitride (CN) 2D/2D nanosheet heterostructure decorated with CdS quantum dots (QDs) has been designed, for the first time. Optimized CdS/WS2/CN without another cocatalyst exhibits a significantly enhanced photocatalytic H2 evolution rate of 1174.5 μmol h−1 g−1 under visible‐light irradiation (λ>420 nm), which is nearly 67 times higher than that of the pure CN nanosheets. The improved photocatalytic activity can be primarily attributed to the highly efficient charge‐transfer pathways built among the three components, which effectively accelerate the separation and transfer of photogenerated electrons and holes, and thus, inhibit their recombination. Moreover, the extended light‐absorption range also contributes to excellent photocatalytic efficiency. In addition, the CdS/WS2/CN photocatalyst shows excellent stability and reusability without apparent decay in the photocatalytic H2 evolution within 4 cycles in 20 h. It is believed that this work may shed light on specifically designed 2D/2D nanosheet heterostructures for more efficient visible‐light‐driven photocatalysts.
Sheets gone dotty: Efficient photocatalysts for hydrogen production through water splitting have been achieved by decorating WS2/graphitic carbon nitride (CN) 2D/2D nanosheets with CdS quantum dots. The improved photocatalytic activity can be attributed to the highly efficient charge‐transfer pathways built among the three components.
Backscattering suppression in silicon-on-insulator (SOI) is one of the central issues to reduce energy loss and signal distortion, enabling for capability improvement of modern information processing ...systems. Valley physics provides an intriguing way for robust information transfer and unidirectional coupling in topological nanophotonics. Here we realize topological transport in a SOI valley photonic crystal slab. Localized Berry curvature near zone corners guarantees the existence of valley-dependent edge states below light cone, maintaining in-plane robustness and light confinement simultaneously. Topologically robust transport at telecommunication is observed along two sharp-bend interfaces in subwavelength scale, showing flat-top high transmission of ~10% bandwidth. Topological photonic routing is achieved in a bearded-stack interface, due to unidirectional excitation of valley-chirality-locked edge state from the phase vortex of a nanoscale microdisk. These findings show the prototype of robustly integrated devices, and open a new door towards the observation of non-trivial states even in non-Hermitian systems.
PET hydrolase (PETase), which hydrolyzes polyethylene terephthalate (PET) into soluble building blocks, provides an attractive avenue for the bioconversion of plastics. Here we present the structures ...of a novel PETase from the PET-consuming microbe Ideonella sakaiensis in complex with substrate and product analogs. Through structural analyses, mutagenesis, and activity measurements, a substrate-binding mode is proposed, and several features critical for catalysis are elucidated.
Objective
To analyze the early complications and causes of oblique lateral interbody fusion, and put forward preventive measures.
Methods
There were 235 patients (79 males and 156 females) analyzed ...in our study from October 2014 to May 2017. The average age was 61.9 ± 0.21 years (from 32 to 83 years). Ninety‐one cases were treated with oblique lateral interbody fusion (OLIF) alone (OLIF alone group) and 144 with OLIF combined with posterior pedicle screw fixation through the intermuscular space approach (OLIF combined group). In addition, 137/144 cases in the combined group were primarily treated by posterior pedicle screw fixation, while the treatments were postponed in 7 cases. There were 190 cases of single fusion segments, 11 of 2 segments, 21 of 3 segments, and 13 of 4 segments. Intraoperative and postoperative complications were observed.
Results
Average follow‐up time was 15.6 ± 7.5 months (ranged from 6 to 36 months). Five cases were lost to follow‐up (2 cases from the OLIF alone group and 3 cases from the OLIF combined group). There were 7 cases of vascular injury, 22 cases of endplate damage, 2 cases of vertebral body fracture, 11 cases of nerve injury, 18 cases of cage sedimentation or cage transverse shifting, 3 cases of iliac crest pain, 1 case of right psoas major hematoma, 2 cases of incomplete ileus, 1 case of acute heart failure, 1 case of cerebral infarction, 3 case of left lower abdominal pain, 9 cases of transient psoas weakness, 3 cases of transient quadriceps weakness, and 8 cases of reoperation. The complication incidence was 32.34%. Thirty‐three cases occurred in the OLIF alone group, with a rate of 36.26%, and 43 cases in the group of OLIF combined posterior pedicle screw fixation, with a rate of 29.86%. Fifty‐seven cases occurred in single‐segment fusion, with a rate of 30.0% (57/190), 4 cases occurred in two‐segment fusion, with a rate of 36.36% (4/11), 9 cases occurred in three‐segment fusion, with a rate of 42.86% (9/21), and 6 cases occurred in four‐segment fusion, with a rate of 46.15% (6/13).
Conclusion
In summary, OLIF is a relatively safe and very effective technique for minimally invasive lumbar fusion. Nonetheless, it should be noted that OLIF carries the risk of complications, especially in the early stage of development.
Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with ...non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley-spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.
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•Recent progress on Mn-based catalysts for low temperature SCR de-NOx was reviewed.•Special attention was paid to clarify the various roles played by each component.•The effects of ...supports were emphasized according to the type of supports.•Reaction mechanism and future direction for SCR catalysts were discussed.
Selective catalytic reduction (SCR) technology has been widely used for the removal of NOx from flue gas. However, it is still a challenge to develop novel low-temperature catalysts for SCR of NOx, especially at temperatures below 200°C. This paper reviewed the recent progress on the Mn-based catalysts for low-temperature SCR de-NOx with NH3. Catalysts were divided into four categories, single MnOx, Mn-based multi-metal oxide, Mn-based multi-metal oxide with support, and Mn-based monolith catalyst. In the section of single MnOx, the effects of several factors, such as Mn oxidation state, crystallization state, specific surface area and morphology on catalytic activity were systematically reviewed. In the section of multi-metal oxide catalysts, the various roles played by the components of catalysts were intentionally summarized from four aspects, improving de-NOx efficiency, enhancing N2 selectivity, improving resistance to SO2 and H2O, extending operation temperature window, respectively. Moreover, the newly emerging morphology-dependent nanocatalysts were highlighted at the end of this section. In the introduction of supported metal oxide catalysts, the effects of supports were systematically analyzed according to their types, such as Al2O3, TiO2, carbon materials, etc. Considering the actual operation, Mn-based monolith catalysts were also introduced with regard to monolith supports, such as ceramics, metal wire mesh, etc. Subsequently, NH3-SCR mechanisms at low temperature, including E-R and L-H mechanisms, were discussed. At last, the perspective and the future direction of low-temperature SCR of NOx were proposed.
A kind of circular polarized (CP) stacked dielectric resonator (DR) antenna with wide bandwidth and high gain is presented in this communication. For this design, a two-layer DR with improved ...performance in bandwidth and gain is used as the basic resonator. By further applying it into a stacked design, two similar modes with adjacent resonant frequencies can be merged together, providing a wide axial ratio bandwidth of more than 20%. The single-feed CP operation is achieved by adopting a coupling cross-slot, which is beneficial for fine-tuning and array forming, as compared to multifeed structures. Two design examples working at different frequency bands and for different senses of CP have been presented to demonstrate the effectiveness of the design concept.
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