Electrospinning–etching strategy was employed to synthesize Pt-loaded SnO2 hollow microbelts (Pt_SnO2 HBLs) based chemiresistive-type sensor demonstrating high sensitivity and selectivity toward ...acetone gas. This strategy overcomes a major hurdle toward achieving ubiquitous gas diffusion in electrospun structures, and provides highly porous thin-walled HBLs with large surface area and small crystallites.
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•In situ templating of SnO2 with SiO2 was employed to form Pt-loaded SiO2@SnO2 core–shell microbelts.•Etching away of SiO2 in the Pt-loaded SiO2@SnO2 microbelts yielded Pt-loaded SnO2 hollow microbelts.•The Pt-loaded SnO2 hollow microbelts exhibited good response (Ra/Rg = 93.5) and selectivity toward 2 ppm acetone at 350 °C.
Challenges for ubiquitous diffusion of gas analytes into semiconducting metal oxides (SMOs) based sensing layers have necessitated the introduction of unprecedented synthesis techniques for thin, porous and high-performance gas sensing materials. In this work, electrospinning and calcination were employed to prepare unprecedented SiO2–SnO2 core–shell microbelts (hereinafter referred to as SiO2@SnO2 BLs) followed by etching away of SiO2 in NaOH solution (pH 12) to achieve hollow SnO2 BLs (hereinafter referred to as SnO2 HBLs) with mean crystal size of 14.01 nm, large BET surface area (143.5 m2‧g–1), high porosity (mean pore size of 5.7 nm), and shell thickness of 58.3 ± 11.4 nm. Sensitization of SnO2 HBLs with apoferritin-templated platinum nanoparticles (Pt NPs) enhanced their detection capability toward acetone. Response (defined as Ra/Rg, where Ra and Rg are sensor resistances in air and target gas, respectively) of Pt(0.12 %)_SnO2 HBLs toward 2 ppm acetone was up to 7.8 times higher compared to that of pristine SnO2 HBLs, and exhibited faster response (9.2 s). The Pt(0.12 %)_SnO2 HBLs based sensor indicated a promising long-term stability, and outstanding repeatability of response (Ra/Rg = 93.7 ± 0.89) toward 25 cycles of 2 ppm acetone exposure in a humid environment of 90 % relative humidity. This performance could be attributed to the unique morphology of HBLs, sensitization effects of catalytic Pt NPs, and enlargement of the electron-depleted layer resulting from a Schottky barrier between Pt NPs and SnO2 grains.
Continuous monitoring of hydrogen sulfide (H2S) in human breath for early stage diagnosis of halitosis is of great significance for prevention of dental diseases. However, fabrication of a highly ...selective and sensitive H2S gas sensor material still remains a challenge, and direct analysis of real breath samples has not been properly attempted, to the best of our knowledge. To address the issue, herein, we introduce facile cofunctionalization of WO3 nanofibers with alkaline metal (Na) and noble metal (Pt) catalysts via the simple addition of sodium chloride (NaCl) and Pt nanoparticles (NPs), followed by electrospinning process. The Na-doping and Pt NPs decoration in WO3 grains induces the partial evolution of the Na2W4O13 phase, causing the buildup of Pt/Na2W4O13/WO3 multi-interface heterojunctions that selectively interacts with sulfur-containing species. As a result, we achieved the highest-ranked sensing performances, that is, response (R air/R gas) = 780 @ 1 ppm and selectivity (R H2S/R EtOH) = 277 against 1 ppm ethanol, among the chemiresistor-based H2S sensors, owing to the synergistic chemical and electronic sensitization effects of the Pt NP/Na compound cocatalysts. The as-prepared sensing layer was proven to be practically effective for direct, and quantitative halitosis analysis based on the correlation (accuracy = 86.3%) between the H2S concentration measured using the direct breath signals obtained by our test device (80 cases) and gas chromatography. This study offers possibilities for direct, highly reliable and rapid detection of H2S in real human breath without the need of any collection or filtering equipment.
Ex‐solution catalysts, in which a host oxide is decorated with confined metallic nanoparticles, have exhibited breakthrough activity in various catalytic reactions. However, catalysts prepared by ...conventional ex‐solution processes are limited by the low surface area of host oxides, the limited solubility of dopants, and the incomplete conversion of doped cations into metal catalysts. Here, the design of the host oxide structure is reconceptualized using a metal–organic framework (MOF) as an oxide precursor that can absorb a large quantity of ions while also promoting ex‐solution at low temperatures (400–500 °C). The MOF‐derived metal oxide host can readily incorporate metal cations, from which catalytic nanoparticles can be uniformly ex‐solved owing to the short diffusion length in the nano‐sized oxides. The distinct ex‐solution behaviors of Pt, Pd, and Rh, and their bimetallic combinations are investigated. The MOF‐driven mesoporous ZnO particles functionalized with PdPt catalysts ex‐solved at 500 °C show benchmark‐level of acetone oxidation activity as well as acetone‐sensing characteristics by accelerating both oxygen chemisorption and acetone dissociation. Their findings provide a new route for the preparation of highly active catalysts by engineering the architecture and composition of the host oxide to facilitate the ex‐solution process rationally.
The ex‐solution process is reconceptualized with the design of the host oxide structure using a metal–organic framework (MOF) as an oxide precursor. Owing to the structural advantages of the MOF, higher levels of doping and more uniform ex‐solution are enabled. These ex‐solved materials attain a record‐breaking performance in acetone oxidation and acetone‐detection reactions.
Metal‐organic frameworks (MOFs) are promising materials for gas sensing but are often limited to single‐use detection. A hybridization strategy is demonstrated synergistically deploying conductive ...MOFs (cMOFs) and conductive polymers (cPs) as two complementary mixed ionic‐electronic conductors in high‐performing stand‐alone chemiresistors. This work presents significant improvement in i) sensor recovery kinetics, ii) cycling stability, and iii) dynamic range at room temperature. The effect of hybridization across well‐studied cMOFs is demonstrated based on 2,3,6,7,10,11‐hexahydroxytriphenylene (HHTP) and 2,3,6,7,10,11‐hexaiminotriphenylene (HITP) ligands with varied metal nodes (Co, Cu, Ni). A comprehensive mechanistic study is conducted to relate energy band alignments at the heterojunctions between the MOFs and the polymer with sensing thermodynamics and binding kinetics. The findings reveal that hole enrichment of the cMOF component upon hybridization leads to selective enhancement in desorption kinetics, enabling significantly improved sensor recovery at room temperature, and thus long‐term response retention. This mechanism is further supported by density functional theory calculations on sorbate–analyte interactions. It is also found that alloying cPs and cMOFs enables facile thin film co‐processing and device integration, potentially unlocking the use of these hybrid conductors in diverse electronic applications.
Described in this study is a hybridization strategy combining conductive metal‐organic frameworks (MOFs) and polymers for improved gas sensing. Significant enhancements in sensor recovery kinetics, cycling stability, and dynamic range at room temperature are demonstrated. Mechanistic insights into energy band alignments and sorbate–analyte interactions reported here are promising toward future high‐performance chemiresistors as well as novel electronic devices based on polymer/MOF composites.
Flexible and mechanically robust gas sensors are the key technologies for wearable and implantable electronics. Herein, the authors demonstrate the high‐performance, flexible nitrogen dioxide (NO2) ...chemiresistors using a series of n‐type conjugated polymers (CPs: PNDIT2/IM‐x) and a polymer dopant (poly(ethyleneimine), PEI). Imine double bonds (C = N) are incorporated into the backbones of the CPs with different imine contents (x) to facilitate strong and selective interactions with NO2. The PEI provides doping stability, enhanced electrical conductivity, and flexibility. As a result, the NO2 sensors with PNDIT2/IM‐0.1 and PEI (1:1 by weight ratio) exhibit outstanding sensing performances, such as excellent sensitivity (ΔR/Rb = 240% @ 1 ppm), ultralow detection limit (0.1 ppm), high selectivity (ΔR/Rb < 8% @ 1 ppm of interfering analytes), and high stability, thereby outperforming other state‐of‐the‐art CP‐based chemiresistors. Furthermore, the thin film of PNDIT2/IM‐0.1 and PEI blend is stretchable and mechanically robust, providing excellent flexibility to the NO2 sensors. Our study contributes to the rational design of high‐performance flexible gas sensors.
In this study, a high‐performance flexible NO2 chemiresistor (IM‐x/P‐y) is developed based on n‐type conjugated polymers containing imine bonds in the backbone. Excellent overall sensing performances with ultralow limit of detection (LOD) are demonstrated.
This work is focused on the development of a surface plasmon-induced visible light active photocatalyst system composed of silica–titania core–shell (SiO2@TiO2) nanostructures decorated with Au ...nanoparticles (Au NPs). The influence of size and distribution of Au NPs on photocatalysis, its fabrication methods, and exploration of the mechanism of visible light activity were investigated. A favorable architecture of SiO2 beads with a thin layer of TiO2 was decorated with Au NP arrays having different size and areal density. Surface modification of SiO2@TiO2 leads to a viable and homogeneous loading of Au NPs on the surface of TiO2, which renders visible light-induced photocatalytic activity on the whole TiO2 surface. An optimized system employing Au NP arrays with 15 nm size and 700/μm2 density showed best catalytic efficiency due to a synergistic effect of the firm contact between Au NPs and TiO2 and efficiently coupled SPR excitation. A brief mechanism relating the electron transfer from surface-plasmon-stimulated Au NPs to the conduction band of TiO2 is proposed.
Lung stem cells are instructed to produce lineage-specific progeny through unknown factors in their microenvironment. We used clonal 3D cocultures of endothelial cells and distal lung stem cells, ...bronchioalveolar stem cells (BASCs), to probe the instructive mechanisms. Single BASCs had bronchiolar and alveolar differentiation potential in lung endothelial cell cocultures. Gain- and loss-of-function experiments showed that BMP4-Bmpr1a signaling triggers calcineurin/NFATc1-dependent expression of thrombospondin-1 (Tsp1) in lung endothelial cells to drive alveolar lineage-specific BASC differentiation. Tsp1 null mice exhibited defective alveolar injury repair, confirming a crucial role for the BMP4-NFATc1-TSP1 axis in lung epithelial differentiation and regeneration in vivo. Discovery of this pathway points to methods to direct the derivation of specific lung epithelial lineages from multipotent cells. These findings elucidate a pathway that may be a critical target in lung diseases and provide tools to understand the mechanisms of respiratory diseases at the single-cell level.
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•Lung endothelial cells control lung stem cell differentiation•In vitro expansion and multilineage differentiation of single lung stem cells•Endothelial TSP1 is required for alveolar differentiation and lung regeneration•BMP4 induces lung-specific, calcineurin/NFATc1-dependent TSP1 expression
3D organoid lung cultures reveal a mechanism by which lung endothelial cells instruct lung stem cells to differentiate into a particular lineage, opening up potential avenues for stimulating these stem cells in response to respiratory-disease-associated injury.
Virtual screening is becoming a ground-breaking tool for molecular discovery due to the exponential growth of available computer time and constant improvement of simulation and machine learning ...techniques. We report an integrated organic functional material design process that incorporates theoretical insight, quantum chemistry, cheminformatics, machine learning, industrial expertise, organic synthesis, molecular characterization, device fabrication and optoelectronic testing. After exploring a search space of 1.6 million molecules and screening over 400,000 of them using time-dependent density functional theory, we identified thousands of promising novel organic light-emitting diode molecules across the visible spectrum. Our team collaboratively selected the best candidates from this set. The experimentally determined external quantum efficiencies for these synthesized candidates were as large as 22%.
Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to ...be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO2 heterostructure. With the ultrahigh specific surface area (54.29 m2 g–1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO2. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO2 nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situ TEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.
Designing an efficient and stable hole transport layer (HTL) material is one of the essential ways to improve the performance of organic-inorganic perovskite solar cells (PSCs). Herein, for the first ...time, an efficient model of a hole transport material (HTM) is demonstrated by optimized doping of a conjugated polymer TFB (poly(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(
N
-(4-
sec
-butylphenyl)diphenylamine)) with a non-hygroscopic p-type dopant F4-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) for high-efficiency PSCs. The PSC with the F4-TCNQ doped TFB exhibits the best power conversion efficiency (PCE) of 17.46%, which surpasses that of the reference devices,
i.e.
, 16.64 (LiTFSI + TBP-doped Spiro-OMeTAD as the HTM) and 11.01% (LiTFSI + TBP-doped TFB as the HTM). F4-TCNQ doped TFB was believed to favor efficient charge and energy transfer between the perovskite and the hole transport layer and to reduce charge recombination as evidenced by steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis. Moreover, the hydrophobic nature of F4-TCNQ contributed to enhancing the stability of the device under ambient conditions with a RH of 45%. The device reported herein retained
ca.
80% of its initial efficiency after 10 days, significantly superior to both LiTFSI + TBP-doped Spiro-OMeTAD (
ca.
30%) and LiTFSI + TBP-doped TFB (
ca.
10%) based counterparts. This simple yet novel strategy paves the way for demonstrating a promising route for a wide range of highly efficient solar cells and other photovoltaic applications.
Designing an efficient and stable hole transport layer (HTL) material is one of the essential ways to improve the performance of organic-inorganic perovskite solar cells (PSCs).
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