Boyuan Xue,Qian Yang,Kaidong Xia,Zhihong Li,George Y. Chen,Dayi Zhang,Xiaohong Zhou
Heavy metals, notably Pb 2+ and Cu 2+ , are some of the most persistent contaminants found in groundwater. Frequent monitoring of these metals, which relies on efficient, sensitive, cost-effective, and reliable methods, is a necessity. We present a nanocomposite-based miniaturized electrode for the concurrent measurement of Pb 2+ and Cu 2+ by exploiting the electroanalytical technique of square wave voltammetry. We also propose a facile in situ hydrothermal calcination method to directly grow binder-free mesoporous NiO on a three-dimensional nickel foam, which is then electrochemically seeded with gold nanoparticles (AuNPs). The meticulous design of a low-barrier Ohmic contact between mesoporous NiO and AuNPs facilitates target-mediated nanochannel-confined electron transfer within mesoporous NiO. As a result, the heavy metals Pb 2+ (0.020 mg·L −1 detection limit; 2.0–16.0 mg·L −1 detection range) and Cu 2+ (0.013 mg·L −1 detection limit; 0.4–12.8 mg·L −1 detection range) can be detected simultaneously with high precision. Furthermore, other heavy metal ions and common interfering ions found in groundwater showed negligible impacts on the electrode’s performance, and the recovery rate of groundwater samples varied between 96.3% ± 2.1% and 109.4% ± 0.6%. The compactness, flexible shape, low power consumption, and ability to remotely operate our electrode pave the way for onsite detection of heavy metals in groundwater, thereby demonstrating the potential to revolutionize the field of environmental monitoring.
Bo Zhang,Hui Wang,Yiwei Lu,Yang Song,Yanlin Li,Yuanyuan Tian
Fabrication of electrochromic films with micro/nanostructures is one of the most feasible ways to improve their properties for high-performance electrochromic devices (ECDs). In this work, mesoporous TiO 2 and NiO electrochromic films are prepared by sol-gel technique with an auxiliary solvent of F108 (PEO 1 3 2 PPO 5 0 PEO 1 3 2 ). By adjusting the content of F108 and heat treatment temperature, the transparent and uniform mesoporous films are successfully prepared. The TiO 2 and NiO films are composed of inter-connected nanoparticles with a size of about 20 nm. The thicknesses of the films are about 300 nm and the mesoporous sizes are about 13 nm. The films have a short response time during the electrochromic process. When supplied with positive/negative voltages for 50 s, the coloring/bleaching times of TiO 2 and NiO mesoporous films are 15/13 and 17/12 s, respectively. The ECD fabricated with TiO 2 and NiO mesoporous films shows good electrochromic properties: short response time (14/19 s, for bleaching/coloring time), wide transmittance modulation range ( ∼ 37.21% at 540 nm), high coloration efficiency (CE) (100.6 cm 2 /C at 540 nm) and outstanding cycle stability (800 cycles). These are attributed to the mesoporous channels of films, which can increase reaction activity site, shorten ions transport path, and thus improve electrochromic reaction.
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