Penner Group Lunch, August 6, 2021.
Lunch at Super A's in honor of Dr. Jihoon Shin (SKKU). Seated, counter-clockwise from back left: Nick Drago, Nick Humphrey, Heriberto Zuleta-Flores, Dr. Jihoon Shin and his wife, Ilektra Andoni, Joe Gonzales, Reg, Josh Ziegler, and Eric Choi. Missing: Ana-Theresa Mendoza.

Investigating the Degradation of Nb2O5 Thin Films Across 10,000 Lithiation/Delithiation Cycles
Ilektra Andoni, Joshua M. Ziegler, Gaurav Jha, Chaitanya Avinash Gadre, Heriberto Flores-Zuleta, Sheng Dai, Shaopeng Qiao, Mingjie Xu, Vivian T. Chen, Xiaoqing Pan*, and Reginald M. Penner*

ACS Applied Energy Materials (2021) Accepted.

Nb2O5 films prepared by electrophoretic deposition and subjected to repetative lithiation/delithiation cycling, degrade by a surprisingly reproducible process: Irreversible capacity (Csp) loss starts at 1000 cycles from a baseline specific capacity of 400 F/g. A gradual reduction of Csp occurs during the ensuing 9000 cycles after which the Csp stabilizes at 200 F/g. We investigate this degradation using six ex-situ instrumental methods and more than 100 individual Nb2O5 films to characterize and understand the composition, atomic scale structure, chemical bonding, electrochemical, and electrical properties of these films during these 10,000 cycles. What emerges is a multi-dimensional picture of the degradation process in which the decline in Csp occurs concurrently with an increase in the charge transfer resistance, a loss of crystalline order, and the dissolution of niobium from the film.

Apurva with Reg and Peter, June 13, 2021.
Apurva finally gets to graduate (officially).

Enhancing the Sensitivity of the Virus BioResistor by Over-Oxidization: Detecting IgG Antibodies
Apurva Bhasin&, Eric J. Choi&, Nicholas P. Drago&, Jason E. Garrido, Emily C. Sanders, Jihoon Shin, Ilektra Andoni, Dong-Hwan Kim, Lu Fang, Gregory A. Weiss*, and Reginald M. Penner*
(2021) Analytical Chemistry, (2021) Submitted.

The Virus BioResistor (VBR) is a biosensor capable of the rapid and sensitive detection of small protein disease markers using a simple dip-and-read modality. For example, the bladder cancer-associated protein DJ-1 (22 kDa) can be detected in human urine within 1.0 min. with a limit-of-detection (LOD) of 10 pM. The VBR uses engineered virus particles as receptors to recognize and selectively bind the protein of interest. These virus particles are entrained in a conductive poly(3,4 ethylenedioxythiophene) or PEDOT channel. The electrical impedance of the channel increases when the target protein is bound by the virus particles. But VBRs exhibit a sensitivity that is inversely related to the molecular weight of the protein target. Thus, large proteins, such as IgG antibodies (150 kDa), can be undetectable even at high concentrations. We demonstrate that the electrochemical over-oxidation of the VBR's PEDOT channel increases its electrical impedance, conferring enhanced sensitivity for both small and large proteins. Over-oxidation makes possible the detection of two an antibody, undetectable at a normal VBR, with a limit-of-detection of 40 ng/mL (250 pM), and a dynamic range for quantitation extending to 600 ng/mL.

Team VBR, May 15, 2021.
Team VBR, celebrating another successful VBR demonstration. From left: Dr. Apurva Bhasin (PhageTech Inc), Eric Choi, and Dr. Jihoon Shin (SKKU, Korea). Not shown: Nick Drago.

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© 2021, Reginald M. Penner