Simetri (United States)

Abstract While fluoride ions (F−) are abundant across environmental and biological systems, common procedures and potentiometric sensors for quantifying aqueous F− are inefficient, time‐consuming, and suffer from poor pH resiliency and high detection limits. Herein, this work reports a new di‐boronic acid‐functionalized ferrocene (FDBA) molecular receptor for noncovalent F− recognition, toward the development of a solid‐state miniaturized voltammetric fluoride sensor capable of direct and reversible F− detection in drinking water (DW) (pH 6) and community water (pH 7.6–9.1) over the µg L−1–mg L−1 range. The associated sensing mechanism is enabled by the conformational change of FDBA from the open (charge‐repelled) to closed (π‐dimerized) conformation, which is facilitated by the unique linkage of two electron‐accepting phenylboronic acid moieties with the electron‐donating ferrocene moiety using rigid conjugated amide linkers. The square wave voltammetric (SWV) oxidation current response of the FDBA‐based fluoride sensor is spectroscopically investigated, suggesting a combination of electrooxidation‐triggered conformational change of FDBA on a nanocarbon‐modified electrode, F− anion–π interactions, and resulting electron transfer between F− and FDBA. The performance of the voltammetric fluoride sensor is compared to that of a commercial liquid junction‐based fluoride ion‐selective electrode (F‐ISE), and of a solid‐contact (SC) F‐ISE sensor chip, demonstrating significant advantages versus traditional potentiometric F‐ISEs.

Analytical methods to rapidly detect explosive compounds with high precision are paramount for applications ranging from national security to environmental remediation. This report demonstrates two proof-of-concept electroanalytical methods for the quantification of 2,4-dinitroanisol (DNAN) and pentaerythritol tetranitrate (PETN). For the first time, DNAN reduction was analyzed and compared at a bare graphitic carbon electrode, a polyaniline-modified (PANI) electrode, and a molecularly imprinted polymer (MIP) electrode utilizing PANI to explore the effect of surface-area and preconcentration affinity on the analytical response. Since some explosive compounds such as PETN are not appreciably soluble in water (<10 μg/L), necessitating a different solvent system to permit direct detection via electrochemical reduction. A 1,2-dichloroethane system was explored as a possibility by generating a liquid-liquid extraction-based sensor exploiting the immiscibility of 1,2-dichloroethane and water. The reduction process was explored using a scan rate analysis to extract a diffusion coefficient of 6.67 x 10⁻⁶ cm/s, in agreement with literature values for similarly structured nitrate esters. Once further refined, these techniques may be extended to other explosives and combined with portable electrochemical hardware to bring real-time chemical information to soldiers and citizens alike.

Bu çalışmada Okun Yasasının geçerliliği Türkiye için ele alınmış ve ekonomik büyüme ile işsizlik arasındaki asimetrik ilişki incelenmiştir. Çalışmada Okun Yasasındaki asimetrinin analiz edilmesinin önemli olduğu düşünülmüş ve bu nedenle Türkiye ekonomisindeki çıktı açıklarının işsizlik oranı üzerindeki etkisi 2005-2020 dönemi için NARDL yöntemi kullanılarak incelenmiştir. Çalışma sonuçlarına göre Türkiye için Okun Yasasının geçerli olduğu tespit edilmiş ve ekonomik büyüme ile işsizlik arasında kısa dönemde asimetrik, uzun dönemde ise simetrik bir ilişkinin var olduğu sonucuna ulaşılmıştır.