(7dh) Interaction of Nanostructures Leads to Macroscopic Behaviors: Towards Designing Multiple-Component Nanostructures with Functionalities for Energy-Related Applications

Lawrence Berkeley National Laboratory, Berkeley, CA, USA March 2015-Current

• Designing Metal Organic Framework/Polymer Films and Graphene Derivative Systems as Scalable Barrier Layers for Enhanced Protection on Photovoltaics
• Hybrid Nanocomposites/Superlattices for Solar Energy Conversion
• Designing Iron Oxide-Metal Organic Framework Superstructures by Ligand-mediated Self-assembly
• Pt-Iron Oxide Hetero-nanostructures with Enhanced Electron Transfer for Photocatalysis

PhD Dissertation: “Semiconductor nanocrystals for photocatalytic hydrogen generation” 2015

Advisor: Prof. Todd D. Krauss (University of Rochester)

Background and Research Interests:

Designing nanostructures with desired functionalities for energy-related applications has always been a central aim of research in nanotechnology. While facing the challenges of finding a catalytic system with good activity, selectivity, and durability, especially under visible light, researchers have put tremendous effort into designing suitable materials or systems. My research aims to solve this problem via developing multiple-component nanostructure systems and understanding key chemical/physical properties as well as inter-component coupling interactions. Through this approach, it is possible to enable rational optimization and practical application of these materials.

Homogeneous systems for light-driven reduction of protons to H₂ typically suffer from short lifetimes because of decomposition of the light-absorbing molecule. A complementary approach would be to incorporate semiconductor nanocrystals, into the system. We recently found a robust and highly active system for photocatalytic hydrogen generation in water that uses CdSe nanocrystals capped with dihydrolipoic acid (DHLA) as the solar energy harvester and a soluble Ni²⁺-DHLA catalyst for proton reduction. In order to understand the mechanism of photo-induced electron transfer in the system, I compared photocatalytic H₂ production for core CdSe nanocrystals to other more highly engineered nanoparticle systems such as core/shell CdSe/CdS nanocrystals and CdSe/CdS dot-in-rod nanoparticles, achieving a result suggesting that surface charge density plays an important role in charge transfer and ultimately hydrogen production activity. The ultrafast transient absorption spectroscopy studies of electron transfer from the CdSe nanocrystals to the Ni²⁺-DHLA catalysts reveal extremely fast electron transfer, providing a fundamental explanation for the previous experimental results of photocatalytic H₂ production.

The above is a summary of work from my PhD on semiconductor nanocrystals-based homogenous photocatalysis. During my post-doctoral study, conducted at the Molecular Foundry at Lawrence Berkeley National Laboratory (advisor Dr. Jeffrey J. Urban), I have enlarged my research scope to cover an extensive variety of materials including inorganic nanoparticles, graphene derivatives, MOFs, and polymers. Using all of these types of materials, I fabricated multiple-component nanostructures/superstructures through self-assembly and atomic layers deposition.

In the future, my efforts will be focused on crossing the traditional boundaries of materials science, chemical engineering, chemistry and nanotechnology. With broad experience in synthesis, fundamental understanding of charge transport and photocatalysis, my future research will focus on three different categories: (1) Synthesis and self-assembly of multifunctional nanostructures. (2) Multiple-component nanostructures for solar energy conversion. (3) New materials and devices for energy storage.

Teaching Interests: With a background in physics, chemistry, and nanomaterials, I would be interested in teaching materials related courses, thermodynamics and nanomaterials engineering. Further, I would like to develop some courses on the interface between science and engineering.

Selected Publications:

1. Zhiji Han*, Fen Qiu*, Richard Eisenberg, Patrick L. Holland, Todd D. Krauss. “Robust Photogeneration of H₂ in Water Using Semiconductor Nanocrystals and a Nickel Catalyst” Science 2012, 338, 6112, 1321-1324 (* equally contributed)

2. Fen Qiu, Zhiji Han, Jeffrey J. Peterson, Michael Y. Odoi, Kelly L. Sower, Todd D. Krauss. “Photocatalytic Hydrogen Generation by CdSe/CdS Nanoparticles” Nano Lett. 2016, 9, 5347-5352

3. Cunming Liu, Fen Qiu, Jeffrey Peterson, Todd D. Krauss. “Aqueous Photogeneration of H₂ with CdSe Nanocrystals and Nickel Catalysts: Electron Transfer Dynamics” J. Phys. Chem. B 2015, 119, 7349-7357

4. Eun Seon Cho, Fen Qiu, Jeffrey J. Urban “Polymer Size and Solvent Effects on Mg Nanocrystal Growth in the Composite” Small 2017, 13, 1602572

5. Fen Qiu, Jun Feng, Dequn Wu, Xianzheng Zhang, Renxi Zhuo. “Nanosized Micelles Self-Assembled from amphiphilic dextran-graft-methoxypolyethylene glycol/poly(ε -caprolactone) copolymer” Eur. Polym. J. 2009, 45, 4, 1024-1031

6. Gregory Pilgrim, Joanne Leadbetter, Fen Qiu, Anni Siitonen, Steven Pilgrim, Todd D. Krauss. “Electron Conductive and Proton Permeable Vertically Aligned Carbon Nanotube Membranes” Nano Lett. 2014, 14, 4, 1728-1733

7. Youn Jue Bae, Eun Seon Cho, Fen Qiu, Daniel T. Sun, Teresa E. Williams, Jeffrey J. Urban, Wendy L. Queen “Transparent Metal-Organic Framework/Polymer Films as Water Vapor Barriers” ACS Appl. Mater. Interfaces 2016, 8, 10098-10103