Abbreviations: LOD = limit of detection, BP = black phosphorus, NRs = nanoribbons, CNT = carbon nanotubes, AAO = anodic aluminum oxide, HT = hydrothermal synthesis, CVD = chemical vapor deposition, OTS = octadecyltrichlorosilane, DEP = dielectrophoresis, CR = chemiresistive, AM = amperometric, FET = field-effect transistor, AQP4 = aquaporin-4, HER2 = human epidermal growth factor receptor 2, PSA = prostatespecific antigen, NPY = neuropeptide Y, DHEAS = dehydroepiandrosterone sulfate, HCHO = formaldehyde, THC = tetrahydrocannabinol, N/A = information not available, and τ res / τ rec = reported or estimated response time/recovery time.

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A single platinum nanowire (PtNW) chemiresistive sensor for ethylene gas is reported. In this application, the PtNW performs three functions: (1) Joule self-heating to a specified temperature, (2) in situ resistance-based temperature measurement, and (3) detection of ethylene in air as a resistance change. Ethylene gas in air is detected as a reduction in nanowire resistance by up to 4.5% for concentrations ranging from 1 to 30 ppm in an optimum NW temperature range from 630 to 660 K. This response is rapid (30−100 s), reversible, and reproducible for repetitive ethylene pulses. A threefold increase in signal amplitude is observed as the NW thickness is reduced from 60 to 20 nm, commensurate with a signal transduction mechanism involving surface electron scattering.

The aim of this work was to develop a simple, accessible, and point-of-use sensor to measure heavy metal ions in water in low-resource areas that cannot accommodate expensive or technical solutions. This report describes a new bipolar electrochemical sensor platform that reimagines conventional anodic stripping voltammetry in a wireless bipolar format with an optical electrochemiluminescent readout that can be quantified with any simple optical sensor like that found on most modern cell phone cameras. We call this technique as optical anodic stripping. Using a new nonlithographic fabrication process, devices could be produced rapidly and simply at <$1/sensor. The sensing scheme was developed, characterized, and optimized using electrochemical and optical methods. Quantitation of Pb 2+ in both lab and natural water samples was rapid (2−3 min), accurate, precise, and highly linear in the 25−1000 ppb range and was shown to be sufficiently selective in the presence of other common heavy metal ions such as Cu 2+ , Cd 2+ , and Zn 2+ .