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 (2016), ASAP10.1021/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. Her preliminary characterization of this extraordinary cycle stability is described in this Letter.

Lithographically Patterned PEDOT Nanowires for the Detection of Iron(III) with Nanomolar Sensitivity

Lindsay R. Kindra, Crystin J. Eggers, Andrew T. Liu, Kelly Mendoza, Jennifer Mendoza, Aviva R. Klein Myers, and Reginald M. Penner*
Analytical Chemistry 87 (2015) 11492.10.1021/acs.analchem.5b03255

Lindsay and coworkers describe the preparation and properties of DFA-doped PEDOT films and nanowires for the detection of Fe(III) in high ionic-strength aqueous solutions. An array of 200 PEDOT-DFA nanowires is far superior for this purpose, relative to a film, enabling the detection of Fe(III) across the range from [Fe(III)] = 10-7 to 10-4 M. A limit of detection is estimated to be 340 pM. The sensitivity of these nanowire arrays for Fe(III) is superior to that provided by ISEs and all other electrical-based sensors, including chemFETs and other types of chemiresistors. Remarkably, PEDOT-DFA nanowire chemiresistors are also label-free and do not require the use of an added redox couple.

A 30 micron Coaxial Nanowire Photoconductor Enabling Orthogonal Carrier Collection

Qiang Xu, Shaopeng Qiao, Rajen Dutta, Zhengyun Wu, and Reginald M. Penner*
Nano Letters 15 (2015) 5861.10.1021/acs.nanolett.5b01941

The bandwidth and sensitivity of photoconductors increases as the distance between the electrical contacts decreases. This is bad since increasing the performance of the photodetector, requires that the photoactive area of the detector be diminished. Qiang envisioned a new architecture for a photoconductive nanowire in which the electrical contacts are an integral part of the nanowire. This enables the photoactive area to be decoupled from the electrical pathlength in the absorber material (CdSe in this case). Qiang is able to achieve excellent metrics for light detection including a photoconductive gain of 2200, a photocurrent response and recovery times of 10 and 100 microseconds, respectively, and a responsivity of 209 A/W.

In-situ Electrical Conductivity of LixMnO2 Nanowires as a Function of "x" and Size.

Mya Le, Yu Liu, Hui Wang, Rajen Dutta, Wenbo Yan, Xiaowei Li, Yu Liu, John C. Hemminger, Ruqian Wu, and Reginald M. Penner*
Chemistry of Materials 27 (2015) 3494.

Mya addresses two questions that strongly influence the efficiency with which a LixMnO2 nanowire is able to function as an energy storage element: First, what is the dc electrical conductance of a LixMnO2 nanowire and the dc conductivity of the LixMnO2 within it as a function of x? Second, what influence, if any, do the lateral dimensions of a nanowire have on these parameters? To answer these two questions, Mya used the LPNE method to prepare arrays of 200 MnO2 nanowires where each nanowire is 40 - 60 nm in height, 275 - 870 nm in width, and 10 microns in length, spanning two gold electrical contacts. The answers are interesting...

Catalytically Activated Palladium@Platinum Nanowires for Accelerated Hydrogen Gas Detection

Xiaowei Li, Yu Liu, John C. Hemminger, and Reginald M. Penner*
ACS Nano, 9 (2015) 3215.

The response/recovery speed of nanoscale chemical sensors is prone to retardation by rate-limiting surfacechemical kinetics because as the critical dimension of the sensor is reduced, the diffusional flux of molecules to sensor surfaces is increased. The performance of nanoscale sensors should therefore be hypersensitive to catalysts. Here Xiaowei has demonstrated that H2 response and recovery kinetics for a highly optimized H2 sensor consisting of a Joule-heated Pd nanowire can be significantly accelerated by the addition of minute quantities (e.g., 1 ML) of a Pt metal catalyst to the nanowire surface..

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