Hasil untuk "Chemistry"

L. S. Darken, R. W. Gurry

K. Venkataraman

O. Sǐnanoğlu, Andrew G. DeRocco

M. Erickson

F. Carey, R. Sundberg

D. Chou

L. Interrante

C. Perrin, Jennifer B. Nielson

Shanshan Zhao, Mingjiang Zhang, Anqi Li et al.

Abstract Visualization in complex, extreme environments necessitates that the imaging material/system to deliver more comprehensive information and endures external mechanical deformation. Endowing polarization, for example, helicity, in adaptable optical materials—to construct circular-polarization-enabled imaging—offers the chance to address the issue. However, retaining considerable luminescence asymmetry during processing while behaving like an elastic rubber remains challenging, resulting from unstable circularly polarized luminescence when deforming existing polarization materials. Here, we propose a covalent cross-linking strategy, combining a sustainable light generator with an optical helicity modulator, to prepare chiroptical network structures exhibiting superior mechanical-chiroptical coupling. The obtained structures provide satisfying circularly polarized luminescence with an asymmetry factor up to 1.31 alongside exceptional tensile strain tolerance, and more importantly, the asymmetry maintains a magnitude of 10−1 even with 80% deformation. We further advance our materials into wearable polarization optical sensors, practicing our developed circular polarization differential imaging in a fire scenario, showing an advancement in imaging resolution compared to other technologies such as thermal, intensity and fluorescence imaging. This covalent-bonding chiroptical network structures enable deformable optical helicity, paving a way for achieving portable imaging identification under extreme conditions.

Michael Daniela Rodriguez-Afanado, Fabian Lopez-Vallejo, Cristian Ochoa-Puentes et al.

Background: The resistance of Mycobacterium tuberculosis (Mtb) on first- and second-line anti-tuberculosis (TB) drugs is an issue for TB control; therefore, developing new anti-TB drugs is a priority in TB research. In this sense, the Ca2+ P-type ATPase plasma membrane transporter CtpF is an interesting anti-TB drug target. Methods: In this work, the activity of 4C-substituted pyrrolo[1,2-a]quinoxalinic compounds on Mtb viability and Ca2+ ATPase activity mediated by the plasma membrane transporter, CtpF, was assessed. The pyrrolo[1,2-a]quinoxalines compounds were initially in silico and analyzed as potential inhibitors of the CtpF transporter. Molecular docking analyses showed that 4-(3,4-methylenedioxyphenyl) pyrrolo[1,2-a]quinoxaline (4b) and 4-(2-chlorophenyl) pyrrolo[1,2-a]quinoxaline (4c) compounds are potential CtpF inhibitors. These compounds were synthesized by green chemistry using deep eutectic solvent under environmentally friendly processes. Results: Even though both compounds, 4b and 4c, inhibit the plasma membrane Ca2+ ATPase activity mediated by the CtpF transporter (IC50 of 8.05 ± 0.04 µM and 9.15 ± 0.03 µM for 4b and 4c, respectively), only the 4b compound was active on Mtb cells (MIC = 25 µg/mL). Interestingly, compound 4b also showed low toxicity on VERO cells (19.65 ± 0.51%) and hemolytic activity (1.45 ± 0.20%) in human O Rh (+) erythrocytes. Conclusions: 4-(3,4-methylenedioxyphenyl) pyrrolo[1,2-a]quinoxalinic core-derived compounds could be useful for developing alternative anti-TB compounds.

Jong Moon Lee, Hung-Vu Tran, Pailinrut Chinwangso et al.

Piezoelectric polymer nanocomposites have attracted substantial interest due to their capability to combine the excellent piezoelectric properties of ceramics with the flexibility of polymers. This combination makes them highly suitable for applications in portable and wearable sensors, as well as energy harvesters. However, their performance is often hindered by inconsistent local piezoelectricity, which results from uneven nanofiller distribution and ineffective stress transfer at the nanofiller/polymer interfaces. Addressing these challenges necessitates improving the dispersibility of nanofillers and enhancing interfacial interactions between nanofillers and the polymer matrix. Additionally, increasing and/or arranging spontaneous polarization in nanofillers can enhance the overall piezoelectricity of nanocomposites, mitigating performance declines. Recent studies aimed at improving the performance of lead-free piezoelectric polymer nanocomposites through nanofiller modifications such as surface coating/decoration and chemical doping have been summarized. The proposed modes of performance enhancement by surface-coated and chemically doped nanofillers have been introduced and summarized. Finally, some suggestions and strategies for future research endeavors are presented.

Denis Lucet, Thierry Le Gall, C. Mioskowski

S. George, A. Ott, J. Klaus

Shajar Abbas, Mushtaq Ahmad, Mudassar Nazar et al.

D. Ehhalt, M. Prather, F. Dentener et al.

N. Krause, A. Hashmi

L. D. Quin

Fengbao Liu, Jinsheng Sun, Xiao Luo

Drilling fluid systems for deep and ultra-deep wells are hampered by both high-temperature downhole environments and lengthy cycle periods. Suppose that the gel particle-plugging agent, the primary treatment agent in the system, fails to offer durable and stable plugging performance. In such a scenario, the borehole wall is susceptible to instability and landslide after prolonged immersion, leading to downhole accidents. In this study, novel core-shell gel particles (modified ZIF) with ZIF particles employed as the core material and organosilicon-modified polyethylene polyamine (PEPA) as the polymer shell were fabricated using PEPA, in-house synthesized (3-aminopropyl) triethoxysilane (APTS), and the ZIF-8 metal-organic framework (MOF) as the raw materials to enhance the long-term plugging performance of gel plugging agents. The modified ZIF particles are nanoscale polygonal crystals and differ from conventional core-shell gel particles in that they feature high molecular sieve catalytic activity due to the presence of numerous interior micropores and mesopores. As a result, modified ZIF exhibits the performance characteristics of both rigid and flexible plugging agents and has an excellent catalytic cross-linking effect on the sulfonated phenolic resin (SMP-3) and sulfonated lignite resin (SPNH) in drilling fluids. Consequently, a cross-linking reaction occurs when SMP-3 and SPNH flow through the spacings in the plugging layer formed by the modified ZIF particles. This increases the viscosity of the liquid phase and simultaneously generates an insoluble gel, forming a particle-gel composite plugging structure with the modified ZIF and significantly enhancing the long-term plugging performance of the drilling fluid.

D. Blake, P. Maness, Zheng Huang et al.

Z. Rappoport