A novel membraneless oxygen sensing nanoprobe was developed based on a hanging drop ionic liquid electrochemical cell. An ultrasmall (<500 nm) working electrode and small volume electrochemical cell allowed for an impressively low detection limit of ∼13 ppm and a response time less than 100 ms, which is unusually fast for an electrochemical gas sensor. The oxygen sensor was stable for hours of operation and, owing to the membraneless design, was easily regenerable when fouled. The pulled capillary form factor of the nanoprobe was found compatible with scanning probe techniques, the demonstration of which was made by application as a tip electrode in gas phase scanning electrochemical microscopy (SECM). In the SECM experiments, the oxygen nanoprobe exhibited micrometer scale spatial resolution with ease. This unique probe design developed here may potentially be engineered into versatile sensors for various volatile molecules other than oxygen, such as those pertinent to hazard analysis and biomedical diagnosis.

Herein, a water-soluble molecular copper complex was investigated as a catalyst for O2 reduction in both water and an organic solvent.

Development of sensing technologies for trace vapors of nitroaromatic compounds (NACs) is highly desired due to the toxic and explosive nature of the target molecules. Here, a NAC sensor based on a membraneless ionic liquid electrochemical cell was developed and applied for room-temperature trace vapor detection. Submicrometer working electrode dimensions yielded maximized portability and cost efficiency and extremely short time scales for molecular identification. The nanoprobe exhibited detection limitscomparable to those of state-of-the-art NAC sensors. The most noteworthy feature was the fast response to trace vapors, allowing for real-time detection of NACs without sample pretreatment. The pulled capillary form factor of the developed sensor enabled its application as tip electrodes in gas-phase scanning electrochemical microscopy (SECM). With the degree of freedom in three dimensions, mapping of the differential vapor pressure of NACs was possible, leading to potential application of the probe in sniffing out the source of explosive gas dissemination.

Redox flow batteries (RFBs) provide an attractive solution for large-scale energy buffering and storage. This report describes the development of nonaqueous RFBs based on trimetallic coordination cluster compounds: [Ru2M­(μ3-O)­(CH3CO2)6(py)3] (M = Ru, Mn, Co, Ni, Zn). The all-ruthenium complex exhibited stable battery cycles in anolyte–catholyte symmetric operation, with rarely observed multielectron storage in a single molecule. Moreover, the complex holds modularly tunable synthetic handles for systematic improvements in solubility and redox potentials. An optimized battery stack containing [Ru3(μ3-O)­(CH3CO2)6(py)3]+ anolyte and [Ru2Co­(μ3-O)­(CH3CO2)6(py)3] catholyte yielded stable cycles with a discharge voltage of 2.4 V, comparable to the state-of-the-art nonaqueous RFBs. Explanation for the exceptional stability of the charged states and prediction of systematic tunability of the redox potentials of the cluster compounds were assisted by DFT calculations.