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Anal Chim Acta ; 1072: 35-45, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31146863


From a safety perspective, it is vital to have fast responding gas sensors for toxic and explosive gases in the event of a gas leak. Amperometric gas sensors have been developed for such a purpose, but their response times are often relatively slow - on the order of 50 seconds or more. In this work, we have developed sensors for hydrogen gas that demonstrate ultra-fast response times. The sensor consists of an array of gold microchannel electrodes, electrodeposited with platinum nanoparticles (PtNPs) to enable hydrogen electroactivity. Very thin layers (∼9 µm) of room temperature ionic liquids (RTILs) result in an extremely fast response time of only 2 s, significantly faster than the other conventional electrodes examined (unmodified Pt electrode, and PtNP modified Au electrode). The RTIL layer in the microchannels is much thinner than the channel length, showing an interesting yet complex diffusion pattern and characteristic thin-layer behavior. At short times (e.g. on the timescale of cyclic voltammetry), the oxidation current is smaller and steady-state in nature, compared to macrodisk electrodes. At longer times (e.g. using long-term chronoamperometry), the diffusion layer is large for all surfaces and extends to the liquid/gas phase boundary, where the gas is continuously replenished from the flowing gas stream. Thus, the current response is the largest on the microchannel electrode, resulting in the highest sensitivity and lowest limit of detection for hydrogen. These microchannel electrodes appear to be highly promising surfaces for the ultrafast detection of hydrogen gas, particularly at relevant concentrations close to, or below, the lower explosive limit of 4 vol-% H2.

Nat Commun ; 5: 3744, 2014 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-24781644


Lab-on-a-chip and miniaturized systems have gained significant popularity motivated by marked differences in material performance at the micro-to-nano-scale realm. However, to fully exploit micro-to-nano-scale chemistry, solvent volatility and lack of reproducibility need to be overcome. Here, we combine the non-volatile and versatile nature of ionic liquids with microcontact printing in an attempt to establish a facile protocol for high throughput fabrication of open microreactors and microfluidics. The micropatterned ionic liquid droplets have been demonstrated as electrochemical cells and reactors for microfabrication of metals and charge transfer complexes, substrates for immobilization of proteins and as membrane-free high-performance amperometric gas sensor arrays. The results suggest that miniaturized ionic liquid systems can be used to solve the problems of solvent volatility and slow mass transport in viscous ionic liquids in lab-on-a-chip devices, thus providing a versatile platform for a diverse number of applications.

Líquidos Iônicos , Dispositivos Lab-On-A-Chip , Análise em Microsséries/métodos , Impressão/métodos , Microfluídica/métodos , Imagem Óptica