Controllable synthesis and formation mechanism of single-crystal β-Co(OH)2 microrings as sensors for detection of nitrite ions

Abstract An easy and low-temperature mixed-solvent method was developed for one-step fabrication of single-crystal β-Co(OH) 2 hexagonal microrings (MRs) by aging in situ generated β-Co(OH) 2 microsheets (MSs) at room temperature for 24–60 h. Dynamic factors (i.e., concentration, water-to-ethanol volume ratio δ , amount of water added, aging temperature, and aging time) were used to control the size and structure of the resulting MRs. β-Co(OH) 2 MRs were easily formed under conditions of low aging temperatures, appropriate δ (3:1–6:1), additional H 2 O, or extended aging. The morphological evolution from microsheets to microrings could be ascribed to the dissolution-diffusion-recrystallization behavior on the (001) facets. The proposed method is simple and environmentally benign. The unique as-obtained β-Co(OH) 2 MRs function as the modified electrode and exhibit excellent sensitivity to NO 2 − . The controllable synthesis of β-Co(OH) 2 MRs with exposed (001) plane offers an effective means for developing layered electrode materials with high sensitivity for detecting nitrite ions.