No abstract

A new coordination polymer of formula [Cd-(C 8 N 2 O 3 H 7 ) 2 (H 2 O) 2 ] n , 1, has been synthesized via the hydrothermal method using a bioinspired ligand, N-nicotinoylglycinate. The compound was characterized by SCXRD, PXRD, FTIR spectra, and thermogravimetric analysis (TGA). Single-crystal Xray diffraction reveals the connectivity between Cd 2+ ions and Nnicotinoylglycinate layers in nature, and the layers are arranged in an ABAB.... fashion to give a three-dimensional packing arrangement stabilized by interlayer N−H•••O and O−H•••O hydrogen bonds and π•••π interactions.An aqueous dispersion of compound 1 exhibits strong emission centered at 420 nm after excitation at 280 nm. This emission has been used for the selective sensing of pxylene over other related electron-rich C 8 aromatic isomers based on luminescence turn-on. The calculated value of the limit of detection (LOD) was 84.55 ppb, which is far lower than the safe limit of p-xylene (300 ppb in water). This compound also shows pH-dependent luminescence properties and stability in a wide range of pH (1−14). In both cases (p-xylene detection and pH dependence), time-resolved studies were used to determine the excited-state lifetime and understand the mechanism of luminescence behavior in the presence of analytes. Density functional theory (DFT)-based computational studies were also carried out to understand the selectivity of detection of p-xylene over the other isomers. Schottky diodes fabricated using this material (CP) showed ideal diode-like behavior at a low voltage regime.

Two new coordination polymers of formulas [Cd2(2,3-pzdc)­(tz)2] (1) and [Cd2(2,3-pzdc)­(dtz)2] (2) {2,3-pzdc = 2,3-pyrazine dicarboxylate, tz = 1,2,4-triazolate, dtz = 3,5-diamino-1,2,4-triazolate)} were synthesized via hydrothermal techniques. Both the compounds were characterized by single-crystal X-ray analysis, powder X-ray diffraction, Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). Single-crystal X-ray analysis shows that both the structures are three-dimensional in nature and connectivity-wise they are similar to each other. In compound 2, the presence of N–H···O hydrogen-bond interactions further stabilized the structure. Aqueous dispersion of both the compounds showed a strong dual emissionone at around 353 nm and another at 369 nm upon excitation at 280 nm. Lifetime studies from time-resolved spectra show 0.82 and 0.60 ns for compound 1 and 2.02 and 1.78 ns for compound 2. The higher lifetimes of the excited states in the case of compound 2 establish the role of hydrogen-bond interactions in reducing the nonradiative decay processes. To explore the junction properties at the Al/material interface of these Schottky barrier diodes, the dark J–V characteristics of both of the devices (ITO/PEDOT/compound 1/Al and ITO/PEDOT/compound 2/Al) were analyzed using the well-known Shockley diode equation. In both the devices (with compound 1 and compound 2), asymmetric behavior is observed under forward and reverse bias, indicating rectification. However, in the compound 2 device, the overall current magnitude is 10 times higher than that of the compound 1 device. The series resistance extracted for the compound 2 device is ≈ 22 times lower than that of the compound 1 device, indicating the higher conductivity of compound 2. This behavior indicates a probable role of hydrogen-bond interactions in the lower resistance and higher conductivity of compound 2 compared to compound 1.

No abstract