Eco-friendly chitosan Schiff base as an efficient sensor for trace anion detection

Herein, a chitosan Schiff base sample (CSAN) was strategically designed and prepared via a two-step process. In the first step, an azo derivative of 1- naphthylamine namely, [2-hydroxy-5-(naphthalene-1-yldiazenyl) benzaldehyde] (HNDB) was synthesized as an aldehyde moiety. Then the condensation reaction of HNDB with chitosan afforded CSAN as the target product. Structural analyses of synthesized material were accomplished through FT-IR, ¹H NMR, UV-Vis, XRD, TGA, and SEM spectral methods. Meanwhile, the heterogeneous CSAN was able to detect the presence of hydrogen carbonate (HCO₃^-), acetate (AcO^-), and cyanide (CN^-) anions in semi-aqueous media (H₂O/DMSO; 10:90%, v/v). Moreover, the selectivity of CSAN towards CN^- anion was increased through variation in solvent mixture ratios. Thereupon, CSAN was explored as a promising sensor towards CN^- anion in an aqueous media through considerable color variation from colorless to pale yellow as well as quantitative chemical analysis. Overall, reliable CSAN chemosensor with high sensitivity for mentioned anions has a pivotal role in practical applications owing to it's reversibility ability.

Modulation of Weak Interactions in Structural Isomers: Positional Isomeric Effects on Crystal Packing and Physical Properties and Solid-State Thin-Film Fabrication

Selective formation of positional isomers and accordingly tuning the physicochemical properties of small conjugated organic molecules through structural isomers is an effective crystal engineering for a fascinating successful delivery of thermally stable and photophysically exciting compounds. By small structural skeleton changes, the single crystal of the naphthalenemaleonitrile isomers is found to exhibit a drastic change in crystal packing array, which in turn is found to tune the thermal and physicochemical properties. The α-isomer (A) forms the "herringbone packing" (HP) due to peri-interaction-sensitive C-H···(Ar)π (Ar = naphthalene ring) interactions, and the β-isomer (B) forms the "bricklayer packing" (BP) due to π(C≡N)···π(Ar) stacking interactions. These two positional isomers have revealed insight of molecular packing-dependent structure-property relationship. In this report, we show that a simple modification of relatively less common weak interactions, such as C-H···π(Ar) ↔ π(C≡N)···π(Ar), through the preparation of isomers, can lead to a drastic change in crystal packing (HP ↔ BP). Also, this report demonstrates that by a small structural diversity, one can obtain significant changes in the physicochemical properties like melting behavior, enthalpy, entropy, and electrical properties in the solid state. Therefore, it transpires from this study that structural isomer provides a useful complement to intermolecular nonbonding interactions as a tool to design new promising materials.

A New Application of Internet of Things and Cloud Services in Analytical Chemistry: Determination of Bicarbonate in Water

In a constantly evolving world, new technologies such as Internet of Things (IoT) and cloud-based services offer great opportunities in many fields. In this paper we propose a new approach to the development of smart sensors using IoT and cloud computing, which open new interesting possibilities in analytical chemistry. According to IoT philosophy, these new sensors are able to integrate the generated data on the existing IoT platforms, so that information may be used whenever needed. Furthermore, the utilization of these technologies permits one to obtain sensors with significantly enhanced features using the information available in the cloud. To validate our new approach, a bicarbonate IoT-based smart sensor has been developed. A classical CO₂ ion selective electrode (ISE) utilizes the pH information retrieved from the cloud and then provides an indirect measurement of bicarbonate concentration, which is offered to the cloud. The experimental data obtained are compared to those yielded by three other classical ISEs, with satisfactory results being achieved in most instances. Additionally, this methodology leads to lower-consumption, low-cost bicarbonate sensors capable of being employed within an IoT application, for instance in the continuous monitoring of HCO₃^- in rivers. Most importantly, this innovative application field of IoT and cloud approaches can be clearly perceived as an indicator for future developments over the short-term.

A diquat-containing macrocyclic anion acceptor in pure water

A self-assembled diquat-containing tetracationic macrocycle is obtained in a high yield, which demonstrates its anion recognition ability in pure water.