High-Performance Room Temperature Ammonia Sensors Based on Pure Organic Molecules Featuring B-N Covalent Bond.

Exploring organic semiconductor gas sensors with high sensitivity and selectivity is crucial for the development of sensor technology. Herein, for the first time, a promising chemiresistive organic polymer P-BNT based on a novel π-conjugated triarylboron building block is reported, showcasing an excellent responsivity over 30 000 (Ra/Rg) against 40 ppm of NH3, which is ≈3300 times higher than that of its B-N organic small molecule BN-H. More importantly, a molecular induction strategy to weaken the bond dissociation energy between polymer and NH3 caused by strong acid-base interaction is further executed to optimize the response and recovery time. As a result, the BN-H/P-BNT system with rapid response and recovery times can still exhibit a high responsivity of 718, which is among the highest reported NH3 chemiresistive sensors. Supported by in situ FTIR spectroscopy and theoretical calculations, it is revealed that the N-H fractions in BN-H small molecule promoted the charge distribution on phenyl groups, which increases charge delocalization and is more conducive to gas adsorption in such molecular systems. Notably, these distinctive small molecules also promoted charge transfer and enhanced electron concentration of the P-BNT sensing polymer, thus achieving superior B-N-containing organic molecules with excellent sensing performance.

Positional Thiophene Isomerization: A Geometric Strategy for Precisely Regulating the Electronic State of Covalent Organic Frameworks to Boost Oxygen Reduction.

With the oxygen conversion efficiency of metal-free carbon-based fuel cells dramatically improved, the building blocks of covalent organic frameworks (COFs) raised principal concerns on the catalytic active sites with indistinct electronic states. Herein, to address this issue, we demonstrate COFs for oxygen reduction reaction (ORR) by regulating the edge-hanging thiophene units, and the molecular geometries are further modulated via positional thiophene isomerization strategy, affording isomeric COF-α with 2-substitution and COF-ß with 3-substitution on the frameworks. The electronic states and intermediate adsorption ability are well-regulated through geometric modification, resulting in controllable chemical activity and local density of π-electrons. Notably, the introduction of thiophene units with different substitution positions into a pristine pure carbon-based COF model COF-Ph achieves excellent activity with a half-wave potential of 0.76 V versus the reversible hydrogen electrode, which is higher than most of those metal-free or metal-based electrocatalysts. Utilizing the combination of theoretical prediction and in situ Raman spectra, we show that the isomeric thiophene skeleton (COF-α and COF-ß) can induce the dangling unit activation, accurately identifying the pentacyclic-carbon (thiophene α-position) adjacent to sulfur atom as active sites. The results suggest that the isomeric dangling groups in COFs are suitable for the ORR with promising geometry construction.

n-Type boron ß-diketone-containing conjugated polymers for high-performance room temperature ammonia sensors.

Organic semiconductor (OSC) gas sensors with good mechanical flexibility have received considerable attention as commercial and wearable devices. However, due to poor resistance to moisture and low conductivity, the improvement in the sensing capability of individual OSCs is limited. Reported here is a promising pathway to construct a series of conjugated organic polymers (COPs) with well-defined pyrimidine (Py-COP) or boron ß-diketone (BF-COP) units. Unlike traditional metal- or carbon-based hybrid materials, the developed COPs can provide abundant absorption sites for gaseous analytes. As a result, the as-prepared BF-COP results in an excellent sensing response of over 1500 (Ra/Rg) toward 40 ppm of NH3 at room temperature, which is the highest value among those of pristine COPs as n-type sensing materials. Notably, they can maintain their initial sensing responses for two months and 90% relative humidity resistance. Combining the results of in situ Fourier transform infrared spectroscopy and theoretical calculations, the ß-diketone skeleton is found to activate the surface electronic environment, verifying that the electron-deficient B ← O groups are adsorption centers. The B/N-heterocyclic decoration effectively modulates the redox properties and electronic interactions, as well as perturbs charge transfer in typical π-conjugated COPs. These results offer insight into developing highly efficient OSC gas sensors, which potentially have broadened sensing applications in the areas of organoboron chemistry.

Long non-coding RNA DLX6-AS1/miR-141-3p axis regulates osteosarcoma proliferation, migration and invasion through regulating Rab10.

Long non-coding RNA (lncRNAs) DLX6-AS1 plays significant roles in various types of malignant tumors, including osteosarcoma (OS), the most prevalent primary malignant bone tumor. However, the role and mechanism of DLX6-AS1 have not been fully illuminated in OS. Here, we aimed to find a novel mechanism for DLX6-AS1 in regulating the development of OS through sponging microRNA (miRNA). According to the luciferase reporter assay, RNA immunoprecipitation and RNA pull-down assay, miRNA (miR)-141-3p can physically interact with DLX6-AS1 and Rab10. The expressions of DLX6-AS1 and Rab10 were upregulated and miR-141-3p was downregulated in OS tissues and cells (MG-63 and U2OS), as described by RT-qPCR and western blotting. Moreover, there was a negative correlation between the expression of miR-141-3p and either DLX6-AS1 or Rab10, and a positive correlation between DLX6-AS1 and Rab10. Functionally, cell proliferation, migration and invasion were evaluated by utilizing the MTT assay and transwell assays. As a result, DLX6-AS1 knockdown suppressed OS cell proliferation, migration and invasion in MG-63 and U2OS cells, which was abolished by the downregulation of miR-141-3p. Similarly, the upregulation of Rab10 not only promoted OS cell progression in vitro, but also blocked the inhibitory effect of miR-141-3p overexpression in OS cells. Notably, DLX6-AS1 knockdown could, in turn, reverse the promoting effect of Rab10 on OS cell progression. Xenograft experiments depicted that DLX6-AS1 knockdown restrained the tumor growth of MG-63 cells in vivo. In conclusion, the knockdown of DLX6-AS1 might suppress OS progression via sponging miR-141-3p and downregulating Rab10, suggesting a novel DLX6-AS1/miR-141-3p/Rab10 pathway in OS progression.

Studies on the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System.

This work is intended to provide a better understanding about the properties and roles of the reaction rim in an alkali-silica reaction. A simplified calcium-alkali-silicate system was created to simulate the multiple interactions among reactive silica, alkaline solution and portlandite near the aggregate surface during the formation and evolution of the reaction rim in an alkali-silica reaction. A transport barrier preventing the migration of calcium and silicate through itself was found on the interface between the alkali silicate and the calcium hydroxide. The barrier was mainly composed of calcium alkali silicate with silicon-oxygen organizations of Q² and Q³ according to the results of 29Si nuclear magnetic resonance, the calcium to silica mole ratio ranging from 0.22 to 0.53 and the alkali to silica ratio ranging from 0.20 to 0.26 based the location of the elemental compositional analysis and the storage period of the system.

Elastic Modulus of the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System Determined by Nano-Indentation.

This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)2 in a chemically-idealized system of the alkali-silica reaction, was studied using nano-indentation. In addition, the corresponding calcium to silica mole ratio of the calcium alkali silicate was investigated. The results show that the elastic modulus of the calcium alkali silicate formed at the interface increased with the increase of the calcium to silica mole ratio and vice versa. Furthermore, the more calcium that was available for interaction with alkali silicate to form calcium alkali silicate, the higher the calcium to silica mole ratio and, consequently, the higher the elastic modulus of the formed calcium alkali silicate. This work provides illustrative evidence from a mechanical point of view on how the occurrence of cracks due to the alkali-silica reaction (ASR) is linked to the formation of the reaction rim. It has to be highlighted, however, that the simplified calcium-alkali-silicate system in this study is far from the real condition in concrete.