2-(1H-Benzimidazol-2-yl)-4,6-dichloro­phenol

The title compound, C13H8Cl2N2O, was prepared by the reaction of 3,5-dichloro-2-hy­droxy­benzaldehyde with 1,2-diamino­benzene in methanol at ambient temperature. The title mol­ecule is essentially planar, the mean deviation from the plane of the non-H atoms being 0.037 (2) Å. There is an intra­molecular O—H⋯N hydrogen bond in the mol­ecule. In the crystal, symmetry-related mol­ecules are linked through N—H⋯O hydrogen bonds, forming polymeric chains propagating in [001]. The chains are linked by π–π inter­actions involving the dichloro­phenol ring and the benzoimidazole ring system [centroid–centroid distances = 3.535 (2) and 3.724 (2) Å]

Humidity Sensing Properties of CuO, ZnO and NiO Composites

The mixed metal oxides were investigated for humidity sensing properties. The composites were prepared by mixing 1:1 mole ratio of CuO-ZnO, CuO-NiO, and NiO-ZnO compound. The samples sintered at 800 oC for 5h, were subjected to do resistance measurements as a function of relative humidity (RH) in the range of 5-98 % and the sensitivity factor was calculated. Among the three composites, CuO-NiO compound possessed the highest humidity sensitivity of 2834.8 while the other two possessed a very low sensitivity factor. The response and recovery of the CuO-NiO composites were 650 and 80 s. X-ray diffraction, and scanning electron microscopy (SEM) was employed to identify the structural phases, and surface morphology of the metal oxide compounds

Humidity Sensing Characteristics of Bi2O3- added TiO2 Composites

The TiO2-Bi2O3 composites heated up to 700 °C for 5 h were characterized by X-ray diffraction, and scanning electron microscopy (SEM) and studied for humidity sensor. The composites were in the mole ratio of 98:2, 95:5, 90:10, 80:20 and 100:0 of TiO2 and Bi2O3 labeled as TOBO-1, TOBO-2, TOBO-3, TOBO-4, and TOBO-5, respectively. The samples sintered at 800 oC for 5h formed a new phase Bi2Ti4O11. The composites were subjected to DC resistance measurements as a function of relative humidity (RH) in the range of 5-98 % and the sensitivity factor was calculated from the relation Sf = R5%/R98% where R5% and R98% were the DC resistances of 5 % and 98 % RH respectively. Among the various composites, TOBO-3 composite possessed the highest humidity response with Sf = 2391.3, while the TOBO-5 and TOBO-2 composites possessed low sensitivity factors of 396.2 and 329.7 respectively. The response and recovery characteristics of the TOBO-3 composite were 420 and 150 s respectively

Approaching Sensitivity of Tens of Ions Using Atomically Precise Cluster–Nanofiber Composites

A new methodology has been demonstrated for ultratrace detection of Hg²⁺, working at the limit of a few tens of metal ions. Bright, red luminescent atomically precise gold clusters, Au@BSA (BSA, bovine serum albumin), coated on Nylon-6 nanofibers were used for these measurements. A green emitting fluorophore, FITC (fluorescein isothiocyanate), whose luminescence is insensitive to Hg²⁺ was precoated on the fiber. Exposure to mercury quenched the red emission completely, and the green emission of the fiber appeared which was observed under dark field fluorescence microscopy. For the sensing experiment at the limit of sensitivity, we have used individual nanofibers. Quenching due to Hg²⁺ ions was fast and uniform. Adaptation of such sensors to pH paper-like test-strips would make affordable water quality sensors at ultralow concentrations a reality