Nanoporous Mixed-Phase In₂O₃ Nanoparticle Homojunctions for Formaldehyde Sensing

Designing a reliable sensor for indoor formaldehyde (HCHO) with high sensitivity and selectivity is crucial for environmental and health protection. This study reported HCHO sensors based on a nanoporous mixed-phase In2O3 nanoparticle. A combined cubic and orthorhombic phase In(OH)3/InOOH [c-In(OH)3/o-InOOH] precursor, synthesized through a facile solvothermal route at different temperatures, was annealed to prepare the In2O3 nanoparticle homojunction. The obtained In2O3, calcined at 350 °C, exhibited a porous structure and a large specific surface area of 81.46 cm3·g–1, facilitating more number of active sites’ exposure for HCHO-sensing reactions. Results showed that the In2O3 calcined at 350 °C exhibited the best HCHO-sensing performances at 120 °C with a large response value (330–50 ppm), good selectivity, and a short response time (12 s). Additionally, its detection limit could reach 11 ppb. This HCHO gas sensing behavior was owing to the mixed-phase homojunction structure formed between cubic and rhombohedral In2O3, the large specific surface area, and the porous structure with abundant oxygen vacancies. This study indicated that the nanoporous mixed-phase In2O3 nanoparticles could be the potential candidates for rapidly detecting HCHO at low concentration levels under low power consumption

α‑Functionalization of 2‑Vinylpyridines via a Chiral Phosphine Catalyzed Enantioselective Cross Rauhut–Currier Reaction

Herein, 2-vinylpyridines as a new type of electron-poor system for the asymmetric cross Rauhut–Currier reaction are reported. 2-Vinylpyridines are chemo- and enantioselectively activated by a newly designed chiral phosphine catalyst. The new reaction provides a powerful synthetic tool for accessing structurally diverse, highly valued chiral pyridine building blocks in good yields and with high enantioselectivities. Preliminary mechanistic studies reveal that two NH protons in the catalyst are critical for the synergistic activation of the substrates and governing the stereoselectivity of this reaction

Direct Access of the Chiral Quinolinyl Core of Cinchona Alkaloids via a Brønsted Acid and Chiral Amine Co-catalyzed Chemo- and Enantioselective α‑Alkylation of Quinolinylmethanols with Enals

A strategy for the facile construction of the chiral quinolinylmethanolic structure, a core featured in cinchona alkaloids, is reported. A new reactivity is harnessed by TfOH-promoted chemoselective activation of α-C–H over O–H bond in quinolinylmethanols. The new reactivity is successfully engineered with an iminium catalysis in a synergistic manner to create a powerful conjugate addition–cyclization cascade process for synthesis of chiral quinoline derived γ-butyrolactones in good yields and with good to excellent enantioselectivities. The method enables the first total synthesis of natural product broussonetine in three steps

Co(OAc)₂‑Catalyzed Trifluoromethylation and C(3)-Selective Arylation of 2‑(Propargylamino)pyridines via a 6-<i>Endo-Dig</i> Cyclization

A Co­(OAc)₂-catalyzed trifluoromethylation and subsequent C(3)-selective arylation of 2-(propargylamino)­pyridines has been developed. A new 6-<i>endo-dig</i> cyclization involving an unprecedented C(3) selective arylation of the pyridines instead of a commonly observed 5-<i>exo-dig</i> cyclization with “N” is realized. Moreover, the study presents the first case of the installation of a trifluoromethyl group into electron-deficient azaarenes. The process delivers an efficient cascade approach to new trifluoromethylated 1,8-naphthyridine structures with a broad substrate scope

Facile Synthesis of Prussian Blue-Filled Multiwalled Carbon Nanotubes Nanocomposites: Exploring Filling/Electrochemistry/Mass-Transfer in Nanochannels and Cooperative Biosensing Mode

We report on mild and selective filling of multiwalled carbon nanotubes (MWCNTs) with Prussian blue (PB) to explore the filling/electrochemistry/mass-transfer in nanochannels and the biosensing mode of nanochannel interior-exterior cooperation. PB-filled MWCNTs (MWCNTs-PB_in) are prepared by filling MWCNTs with the gradually growing PB and then selectively removing the outer-surface PB by careful chemical washing. The prepared MWCNTs-PB_in composites possess high filling yield (mass ratio of PB to MWCNTs, (30 ± 3)%) and electroactivity percentage (mass ratio of electroactive PB to total PB, (45 ± 3)%). The MWCNTs-PB_in composites on Au electrode exhibit strong and stable electrocatalytic activity of filled PB for H₂O₂ reduction and electroanalysis. The filling of the MWCNTs with electroactive PB also provides a new experimental platform to deal with the widely concerned issue of mass transfer inside nanochannels. The normalized cyclic voltammetric responses of filled PB on MWCNTs-PB_in electrode at relatively low scan rates (below 125 and 75 mV s^–1 for mass transfer of K⁺ and K⁺ + H₂O₂, respectively) were found to be equivalent to those of conventionally electrodeposited PB on MWCNTs/Au and Au electrodes, demonstrating that the mass transfer of K⁺ and H₂O₂ inside our MWCNTs is comparable to those outside our MWCNTs at the low scan rates. Furthermore, the unoccupied outer surfaces of MWCNTs-PB_in are conveniently exploited to bind 4-(1-pyrenyl) butyric acid through π–π stacking interaction and then to anchor glucose oxidase or lactate oxidase through the EDC/NHS chemistry. Thus, we have developed a novel cooperative biosensing mode by combining outer-surface biocatalyzed oxidation of substrate with interior PB-catalyzed reduction of enzymatically generated H₂O₂, which endows our biosensors with low detection potential (−0.1 V) and satisfactory sensitivity/selectivity