BiSnO Overlayer Assists Bilayer Chemiresistor in Humidity-Independent and Highly Selective Detection of Expiratory Acetone.

Constructing a bilayer structure has not been reported as a method to mitigate the adverse effect of water poisoning on oxide chemiresistors while simultaneously enhancing gas selectivity and sensitivity. To address this challenge, pyrochlore-BiSnO has been first utilized as an overlayer on a ZnO sensing layer for constructing a bilayer acetone chemiresistor, leading to remarkable improvement in the performance for trace-level (500 p-p-b) acetone detection under high humidity (80% relative humidity). In addition, owing to the catalytic predecompositions of ethanol across the overlayer, an outstanding acetone gas selectivity (/ = 2.

Indoor Air Quality Monitoring System with High Accuracy of Gas Classification and Concentration Prediction via Selective Mechanism Research.

The efficacy of sensors, particularly sensor arrays, lies in their selectivity. However, research on selectivity remains notably obscure and scarce. In this work, indoor pollutants (CH, HCHO, CH, and NO) were chosen as the target gas.

Enzymes on Steroids.

Efficient assembly and functionalization of biologically active steroids continue to pose a significant synthetic hurdle. The mining and engineering of selective P450 C-H hydroxylases combined with chemoenzymatic synthesis furnished a new solution to this challenging problem.

Wearable Gas Sensor Based on Reticular Antimony-Doped SnO/PANI Nanocomposite Realizing Intelligent Detection of Ammonia within a Wide Range of Humidity.

Wearable gas sensors demonstrate broad potential for environmental monitoring and breath analysis applications. Typically, they require a highly stable and high-performance flexible gas sensing unit that can work with a small, flexible circuit to enable real-time accurate concentration analysis and prediction. This work proposes a flexible gas sensor using antimony-doped tin dioxide composite polyaniline as the sensing material for room-temperature ammonia detection over a wide humidity range.

Insights into Stereoselectivity Switch in Michael Addition-Initiated Tandem Mannich Cyclizations and Their Extension from Enamines to Vinyl Ethers.

Both - and - tetracyclic spiroindolines are the core of many important biologically active indole alkaloids, but the divergent synthesis of these important motifs is largely hampered by the limited stereoselectivity control. A facile stereoinversion protocol is reported here in Michael addition-initiated tandem Mannich cyclizations for constructing tetracyclic spiroindolines, providing an easy access to two diastereoisomeric cores of monoterpene indole alkaloids with high selectivity. The mechanistic studies including in situ NMR experiments, control experiments, and DFT calculations reveal that the reaction undergoes a unique retro-Mannich/re-Mannich rearrangement including a C-C bond cleavage that is very rare for a saturated six-membered carbocycle.

Reply to the Comment on "Understanding the Increasing Trend of Sensor Signal with Decreasing Oxygen Partial Pressure by a Sensing-Reaction Model Based on O Species".

In our recent work (, , 1095-1104), Mirabella et al. provided comments on our publication, mainly focusing on the controversy between the oxygen vacancy model and the ionosorbed model and the related derivation based on the law of mass action. Herein we explain the correlation between the ionosorption model and the oxygen vacancy model and provide a brief introduction of our view on these two models.

Multifunctional Flexible Ionic Skin with Dual-Modal Output Based on Fibrous Structure.

Flexible wearable electronic devices with multiple sensing functions that simulate human skin in all aspects have become a popular research topic. However, the current expensive and time-consuming means of integration and the complex decoupling process are hampering the further development of multifunctional sensors. Here, an ultraflexible ionic fiber membrane (IFM) prepared by a simple electrospinning technique is reported, which exhibits pressure and humidity sensing properties.

Allenamide-Initiated Cascade [2+2+2] Annulation Enabling the Divergent Total Synthesis of (-)-Deoxoapodine, (-)-Kopsifoline D and (±)-Melotenine A.

A facile method for the construction of the aspidosperma core from indoles functionalized with a nonterminal N-allenamide and dimethyl methylenemalonate is described. Various polysubstituted tetracyclic spiroindolines (27 examples) were afforded in good yields (61-90 %) with >99/1 dr and >99/1 Z/E selectivity under mild conditions. The annulation reaction provides straightforward access to the tetracyclic spiroindoline skeleton with substituents at the C5 position occurring in many natural products.

All-Nanofiber Network Structure for Ultrasensitive Piezoresistive Pressure Sensors.

Sensing materials with fiber structures are excellent candidates for the fabrication of flexible pressure sensors due to their large specific surface area and abundant contact points. Here, an ultrathin, flexible piezoresistive pressure sensor that consists of a multilayer nanofiber network structure prepared via a simple electrospinning technique is reported. The ultrathin sensitive layer is composite nanofiber films composed of poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) and polyamide 6 (PEDOT:PSS/PA6) prepared by simultaneous electrospinning.

MOF-Derived Mesoporous and Hierarchical Hollow-Structured InO-NiO Composites for Enhanced Triethylamine Sensing.

It remains a challenge to design and fabricate high-performance gas sensors using metal-organic framework (MOF)-derived metal oxide semiconductors (MOS) as sensing materials due to the structural damage during the annealing process. In this study, the mesoporous InO-NiO hollow spheres consisting of nanosheets were prepared via a solvothermal reaction and subsequent cation exchange. More importantly, the transformation of Ni-MOF into In/Ni-MOF through exchanging the Ni ion with In ion can prevent the destruction of the porous reticular skeleton and hierarchical structure of Ni-MOF during calcination.

Selectivity Switch in a Rhodium(II) Carbene Triggered Cyclopentannulation: Divergent Access to Three Polycyclic Indolines.

A selectivity switch in a Rh /carbene-triggered cyclopentannulation with catalytic InCl is reported for the first time, affording both diastereomers of the fused spiroindolines and an unusual bridged tetracyclic indoline in high yields with excellent selectivities. Mechanistic studies indicate an intramolecular annulation of the indole with an in situ formed aminocyclopropane. The stepwise thermal conversions from the kinetic spiroindoline to the metastable bridged indoline, and then to the thermodynamic spiroindoline, involving a ring-opening rearrangement of a cyclopentane, is crucial for selectivity control.

Access to Hexahydrocarbazoles: The Thorpe-Ingold Effects of the Ligand on Enantioselectivity.

A novel cyclization reaction of methylenemalonate with indoles is reported, and it provides efficient access to a variety of hexahydrocarbazoles. The enantioselective version was realized by a finely tuned ligand/Cu catalyst. The optically active hexahydrocarbazoles contain three quaternary carbon centers and are obtained in up to 99 % yield with greater than 99:1 d.

Acetone gas sensor based on NiO/ZnO hollow spheres: Fast response and recovery, and low (ppb) detection limit.

NiO/ZnO composites were synthesized by decorating numerous NiO nanoparticles on the surfaces of well dispersed ZnO hollow spheres using a facile solvothermal method. Various kinds of characterization methods were utilized to investigate the structures and morphologies of the hybrid materials. The results revealed that the NiO nanoparticles with a size of ∼10nm were successfully distributed on the surfaces of ZnO hollow spheres in a discrete manner.

Hierarchical Assembly of α-FeO Nanorods on Multiwall Carbon Nanotubes as a High-Performance Sensing Material for Gas Sensors.

This paper presents a facile hydrolysis reaction and annealing for preparing a novel hierarchical nanoheterostructure via assembly of α-FeO nanorods onto multiwall carbon nanotubes (MWCNTs) backbones. The as-synthesized nanocomposites were characterized using XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and BET (Surface Area and Porosity System). The observations showed uniform α-FeO nanorods approximately 100-200 nm in length and 50-100 nm in diameter that were hierarchically assembled onto the surface of the MWCNTs.

Self-assembled chiral helical nanofibers by amphiphilic dipeptide derived from d- or l-threonine and application as a template for the synthesis of Au and Ag nanoparticles.

The discovery of a class of self-assembling peptides that spontaneously undergo self-organization into well-ordered structures opened a new avenue for molecular fabrication of biological materials. In this paper, the structure controlled helical nanofibers were prepared by two artificial β-sheet dipeptides with long alkyl chains derived from l- and d-threonine (Thr) and sodium hydroxide (NaOH). These helical nanofibers have been characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD).