Celebratory Breakfast at Plums Cafe in Costa Mesa, December 6. Guests of honor included Mya (far left),
Xiaowei (sitting next to her), and Raj (in the red jacket). Crystin couldn't attend!

Sub-6 nm Palladium Nanoparticles For Faster, More Sensitive H2 Detection Using Carbon Nanotube Ropes,

Xiaowei Li, Mya Le Thai, Rajen K. Dutta, Shaopeng Qiao, Girija T. Chandran, and Reginald M. Penner*,
ACS Sensors 2 (2017) 282.10.1021/acs.analchem.6b04840

What is a faster and more sensitive H2 sensor then a Pd nanowire? Pd nanoparticles, dispersed within a carbon nanotube (CNT) rope - but this is true if and only if the Pd nanoparticles are REALLY small - in this case, having a mean diameter of 6 nm or less. Xiaowei first produces a carbon CNT rope by dielectrophoresis, and then uses pulsed electrodeposition to form a high density of these Pd nps within the rope. The performance of these sensors for detecting H2 eclipses nanowire-based sensors, including all those we have developed, since 2001! Congrats Xiaowei!!

A Virus-Enabled Biosensor For Human Serum Albumin,

Alana Ogata, Joshua Edgar, Sudipta Majumdar, Shae Petterson, Jeffrey Briggs, Ming Tan, Stephan T. Kudlacek, Christine Schneider, Gregory A. Weiss* and Reginald M. Penner*,
Analytical Chemistry 89 (2017) 249.10.1021/acs.analchem.6b04840

Working together with her coauthors, Alana has tested a new biosensor that is extremely simple, consisting of a pair of mm-scale gold electrodes (shown here), both of which are coated with virus-PEDOT bioaffinity layers. An impedance measurement between these two electrodes transduces the specific binding of HSA to these layers. HSA concentrations across the physiologically relevant range of 100 nM to 5 microM were detected in buffer and synthetic urine using this biosensor. This biosensor architecture is manufacturable, compatible with small sample volumes (50 microL), and capable of rapid analysis times (below 15 min).

Electrically Transduced Sensors Based on Nanomaterials
(2012 - 2016),

Girija Thesma Chandran, Xiaowei Li, Alana Ogata, and Reginald M. Penner*,
Analytical Chemistry 89 (2017) 249.10.1021/acs.analchem.6b04687

The driver for new analytical science in the area of sensing has been the emergence of new nanomaterials. Prominent trends include the rise to prominence of graphene and its derivatives as transducers, the refinement and diversification of nanostructured metal oxide sensors, the impact of electrospinning on the development of polymer nanowire and nanofiber-based sensor architectures, and the first application of new inorganic 2D nanomaterials in sensors including 2D metal carbides and nitrides (MXenes), 2D layered transition metal dichalcogenides (TMDs), and black phosphorus 2D layers. We review this recent work.

Electrodeposited, Transverse Nanowire Electroluminescent Junctions

Shaopeng Qiao, Qiang Xu, Rajen K. Dutta, Mya Le Thai, Xiaowei Li, and Reginald M. Penner*
ACS Nano 10 (2016) 8333.10.1021/acsnano.6b04022

Shaopeng has discovered a means for electrodepositing and characterizing the electroluminescence (EL) properties of linear arrays of many nearly identical metal-semiconductor-metal junctions. In this paper, he uses this platform to characterize arrays of nickel-(nc-CdSe)-gold M-S-M junctions. These junctions are prepared by first electrodepositing an ensemble of 60 nearly identical nc-CdSe nanowires, and then locating nickel and gold contacts on opposite sides of each nanowire along their axes also using electrodeposition. These devices are termed "transverse nanowire electroluminescent junctions" and they are surprisingly efficient.

100k Cycles and Beyond: Extraordinary Cycle Stability for MnO2 Nanowires Imparted by a Gel Electrolyte

Mya Le Thai, Girija Thesma Chandran, Rajen Dutta, Xiaowei Li, and Reginald M. Penner*
ACS Energy Letters 1 (2016) 57.10.1021/acsenergylett.6b00029

The problem with using nanowires as energy storage materials is their limited cycle stability. Nanowires are susceptible to dissolution and corrosion which rapidly cause a loss of through-wire conduction and irreversible capacity loss. Mya discovered that in the case of MnO2 - an Li+ insertion metal oxide - substituting a liquid electrolyte based on acetonitrile or propylene carbonate (PC) with a viscous PMMA-containing PC electrolyte extends the cycle stability of these nanowires from 5000 cycles to more than 100,000 cycles.

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