Dr. Crystin Eggers and Reg at the UCI Hooding ceremony, Saturday, June 17 (photo credit: Prof. Sergey Nizkorodov).

Supercharging a MnO2 Nanowire: An Amine-Altered Morphology Retains Capacity at High Rates and Mass Loadings

Girija Thesma Chandran, Gaurav Jha, Shaopeng Qiao, Mya Le Thai, Rajen Dutta, Alana F. Ogata, Ji-Soo Jang, Il-Doo Kim, and Reginald M. Penner*,
Langmuir (2017) Just Accepted.10.1021/acs.langmuir.7b00729

Girija studied the influence of hexamethylenetetraamine (HMTA) on the morphology of MnO2 and its properties for electrical energy storage. She prepared arrays of gold@MnO2, core@shell nanowires by electro-deposition with and without the HMTA and evaluated their electrochemical properties. Girija found that HMTA alters the MnO2 in three ways: 1) it creates a more open morphology for the MnO2 coating, 2) the electronic conductivity of the MnO2 is increased by an order of magnitude, and 3) MnO2 prepared in HMTA shows a (001) interlayer spacing that is expanded by 30% possibly accelerating Li transport. The net effect of ''HTMA-doping'' is to dramatically improve high rate performance, culm-inating in an increase in the specific capacity by a factor of up to 15 at 100 mV/s.

Collateral Advantages of a Gel Electrolyte for MnO2 Nanowire Capacitors: Higher Voltage; Reduced Volume,

Mya Le Thai, Shaopeng Qiao, Rajen K. Dutta, Gaurav Jha, Alana Ogata, Girija Thesma Chandran, and Reginald M. Penner*,
ACS Energy Letters 2 (2017) 1162.10.1021/acsenergylett.7b00172

How can 1D nanowires be arranged in 3D to produce powerful capacitors? Mya Le Thai has studied one solution to this problem, involving the preparation of nanowire ``sandwich'' capacitors in which two, 2D arrays of MnO2 nanowires are separated with a ``cream filling'' of PMMA gel electrolyte just 2 microns in thickness. Two conclusions are: 1) The PMMA gel permits the Vmax to be increased by 50% from 1.2 V to 1.8 V, allowing the specific energy to be increased 5-6 fold. and 2) Mya's capacitors exhibit no capacity fade, even when cycled 100,000 cycles across 1.8 V at 200 mV/s.

Celebratory lunch at Eureka!, April 9. Guests of honor included Zenab (left, and front), Girija (5th from left), Prof. Il-Doo Kim from KAIST (7th from left), Won-Tae Koo from KAIST (next to Reg), and Ji-Soo Jang from KAIST (next to Won-Tae).

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.

Two former postdocs with the boss.

Reg, Nate Lewis, and Chengxiang (''CX'') Xiang. CX is principal investigator in the Joint Center for Artificial Photosynthesis (JCAP) at Caltech.

March 23,2017

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