CATEGORY / Research Projects

1. Disordered Inorganic/Polymer Nanoparticle Assemblies

1. Disordered Inorganic/Polymer Nanoparticle Assemblies for Photovoltaic Applications

Kevin Kittilstved (Chemistry) and Dhandapani Venkataraman (Chemistry)

One of the most fundamental criterion for a photovoltaic device is the efficient separation of charges following light absorption to create excitons. The fields of polymer and inorganic solar cells both rely on designing n- and p-type layers and then working hard to organize these possibly immiscible materials into well-ordered structures with defined morphology to form the perfect bulk heterojunction as shown in Fig. 1. Our approach will be to instead use n- and p-type materials composed of inorganic and organic semiconductor nanoparticles that are both smaller than the exciton diffusion lengths in their bulk analogs.

Fig. 1. Schematic representation of binary assemblies of inorganic and polymer semiconductor nanoparticles.

We will prepare new binary nanoparticle superlattices using the general guidelines recently published by the Venkataraman group [1]. The REU students working on this project will implement these design principles to optimize the compatibility of the inorganic nanoparticle surface-capping groups that are expected to play a significant role in controlling the thermodynamics and kinetics of the assembly process.

  • Inorganic Semiconductor Nanocrystals: An REU student in the Kittilstved group will synthesize n-type inorganic semiconductor nanocrystals that will serve as the electron conducting material.
  • Semiconducting Polymer Nanoparticles: An REU student in the Venkataraman group will prepare p-type semiconducting polymer nanoparticles with nanocrystalline domains for solar absorption and hole transport properties.
  • Collaborative Effort: The two REU students will work together to design and optimize methods to prepare binary assemblies with systematic variation of the composition of each component. They will also characterize the assemblies using various physical techniques and electron microscopies.

CITED REFERENCES:

  1. L.A. Renna, C.J. Boyle, T.S. Gehan and D. Venkataraman, “Polymer Nanoparticle Assemblies: A Versatile Route to Functional Mesostructures” Macromolecules, 2015, 48, 6353-6368.

2. Biodistributions of Semiconductor Quantum Dots

2. Biodistributions of Quantum Dots that are Used in Solar Cells

Vincent Rotello (Chemistry) and Richard Vachet (Chemistry)

Quantum dots (QD) are semiconducting nanocrystals that are finding increasing applications in devices such as solar cells [1]. As the use of QDs in solar cells becomes widespread, these nanomaterials will inevitably be released into the environment, and their impact on the health of humans, plants, microbes, and ecological systems could be substantial [2]. Therefore, studies on the environmental impact of QDs are necessary. In particular, studies that relate QD chemical/physical properties to environmental fate, transport, and accumulation are needed [3-5]. In this REU project, students will explore QD stability and how their chemical and physical properties influence biodistributions (Fig. 1).

Fig. 1. Functionalized QD bioavailability

QD stability is important because the core materials of common QDs are selenium and cadmium; the latter of which can be toxic. QD size and surface chemistry are critical parameters that affect their properties in solar cell devices, and these two parameters also control their stability and the availability of the materials in the environment and in biological systems [6,7]. The REU students involved in this project will help obtain quantitative data on the role of size and surface properties on QD stability and biodistributions in model cell-based and animal systems. Specifically, a newly developed approach in our laboratories, which is based on laser desorption/ionization mass spectrometry (LDI-MS), will be further optimized and used [8,9].

  • Design and Synthesis of Model Functionalized Quantum Dots: An REU student in the Rotello group will synthesize QD materials of various sizes and with various chemical functionalities.
  • Develop and Optimize LDI-MS as a Means to Track QDs in Complex Samples.: An REU student in the Vachet group will develop and apply new mass spectrometric methods to track QDs in complex samples.
  • Collaborative Effort: The two REU students will work together and use the model QDs and LDI-MS to investigate the stability and uptake of these materials in cells and animal systems.

CITED REFERENCES:

  1. I. Robel, V. Subramanian, M. Kuno and P.V. Kamat, “Quantum dot solar cells. Harvesting light energy with CdSe nanocrystals molecularly linked to mesoscopic TiO2 films” J Am Chem Soc, 2006, 128, 2385-2393.
  2. R. Hardman, “A toxicologic review of quantum dots: Toxicity depends on physicochemical and environmental factors” Environ Health Persp, 2006, 114, 165-172.
  3. S.J. Klaine, P.J.J. Alvarez, G.E. Batley, T.F. Fernandes, R.D. Handy, D.Y. Lyon, S. Mahendra, M.J. McLaughlin and J.R. Lead, “Nanomaterials in the environment: Behavior, fate, bioavailability, and effects” Environ Toxicol Chem, 2008, 27, 1825-1851.
  4. Z.J. Zhu, P.S. Ghosh, O.R. Miranda, R.W. Vachet and V.M. Rotello, “Multiplexed Screening of Cellular Uptake of Gold Nanoparticles Using Laser Desorption/Ionization Mass Spectrometry” J Am Chem Soc, 2008, 130, 14139-14143.
  5. Z.J. Zhu, V.M. Rotello and R.W. Vachet, “Engineered nanoparticle surfaces for improved mass spectrometric analyses” Analyst, 2009, 134, 2183-2188.
  6. Z.J. Zhu, R. Carboni, M.J. Quercio, B. Yan, O.R. Miranda, D.L. Anderton, K.F. Arcaro, V.M. Rotello and R.W. Vachet, “Surface Properties Dictate Uptake, Distribution, Excretion, and Toxicity of Nanoparticles in Fish” Small, 2010, 6, 2261-2265.
  7. Z.J. Zhu, Y.C. Yeh, R. Tang, B. Yan, J. Tamayo, R.W. Vachet and V.M. Rotello, “Stability of quantum dots in live cells” Nat Chem, 2011, 3, 963-968.
  8. B. Creran, B. Yan, D.F. Moyano, M.M. Gilbert, R.W. Vachet and V.M. Rotello, “Laser desorption ionization mass spectrometric imaging of mass barcoded gold nanoparticles for security applications” Chem Commun, 2012, 48, 4543-4545.
  9. Z.J. Zhu, R. Tang, Y.C. Yeh, O.R. Miranda, V.M. Rotello and R.W. Vachet, “Determination of the Intracellular Stability of Gold Nanoparticle Monolayers Using Mass Spectrometry” Anal Chem, 2012, 84, 4321-4326.

5. Targeting Bacteria for Biosensing and Bioremediation of Oil Spills

5. Targeting Bacteria for Biosensing and Bioremediation of Oil Spills

Lynmarie Thompson (Chemistry) and Mingxu You (Chemistry)

Bacteria have the ability to sense chemicals in their environment and to use this information to direct their swimming. The ability to engineer this chemotaxis process would enable us to develop bacteria as sensors for environmental pollutants and to direct oil-consuming microbes for bioremediation. Our approach to this goal is to use DNA structures to control the assembly of the protein complexes that direct bacterial chemotaxis.

DNA-mediated assembly of chemoreceptor complexes: An REU student in the Thompson lab will link chemotaxis proteins to DNA oligonucleotides. These oligonucleotides will assemble into a DNA structure that positions the chemotaxis proteins to assemble into a functional complex with native geometry.

Aptamer binding-controlled DNA structures: An REU student in the You lab will develop a DNA aptamer for binding a desired target molecule (eg hydrocarbon pollutant). This aptamer will be incorporated into a DNA structure such that ligand binding is required for assembly of the DNA structure

Collaborative effort: The two REU students will work together to demonstrate and optimize the use of the aptamer-linked DNA structure for ligand-controlled assembly of functional chemotaxis complexes.


CITED REFERENCES:

3. Synthesis and Assembly of Nanostructured Polymeric and Hybrid Materials

3. Synthesis and Assembly of Nanostructured Polymeric and Hybrid Materials

Ryan Hayward (Polymer Science & Engineering) and Todd Emrick (Polymer Science & Engineering)

This project will combine new synthetic polymer and nanocomposite materials with self assembly and morphological characterization techniques to produce nanostructured materials that can be implemented in a variety of energy-related devices including membranes, electrodes, optoelectronic devices, solar cells, and light emitting materials.  Previous collaborative research between Emrick and Hayward has focused on connecting p-type and n-type materials in unique architectures that lead to advanced device performance.1-3 REU students involved in this project will develop new polymer materials that combine polymers with tailored architectures, chemical functionalities, and physical properties and will use these novel polymers in assembly techniques designed to generate structures ideal for components of devices. Specific proposed activities include:

Polymer synthesis and characterization: An REU student in the Emrick group will prepare polymers, nanoparticles, and hybrid materials from functional building blocks.

Solution assembly: An REU student in the Hayward group will study processes by which these materials self-assemble using techniques such as X-ray and light scattering, optical spectroscopy, and microscopy.

•  Collaborative Effort: The REU students in each group will collaborate to understand how polymer and nanoparticle structure impacts assembly and device performance.  The students will further benefit from the extensive array of photophysical characterization and device fabrication capabilities within the UMass Amherst facilities.


CITED REFERENCES:

  1. Acevedo-Cartagena, DE., Zhu, JX., Trabanino, E., Pentzer, E., Emrick, T., Nonnenmann, SS., Briseno, AL., Hayward, RC. “Selective nucleation of poly(3-hexyl thiophene) nanofibers on multilayer graphene substrates” ACS Macro Letters, 2015, 4, 483-487. DOI: 10.1021/acsmacrolett.5b00038
  2. Hammer, BAG., Reyes-Martinez, MA., Bokel, FA., Liu, F., Russell, TP., Hayward, RC., Briseno, AL., Emrick, T. “Reversible, self cross-linking nanowires from thiol-functionalized polythiophene diblock copolymers” ACS Applied Materials & Interfaces, 2014, 6, 7705-7711. DOI: 10.1021/am500976w
  3. Lee, CH., Crosby, AJ., Hayward, RC., Emrick, T. “Patterning nanoparticles into rings by ‘2-d Pickering emulsions’” ACS Applied Materials & Interfaces, 2014, 6, 4850-4855. DOI: 10.1021/am405828a

4. Chemical Conversion of Cellulosic Biomass

4. Chemical Conversion of Cellulosic Biomass: Paving the Way for Tomorrow’s Biofuels

Scott Auerbach (Chemistry) and Wei Fan (Chemical Engineering)

Biofuels provide a promising, renewable route to liquid transportation fuels such as gasoline, diesel and jet fuel. Even though utilization of biofuel does produce carbon dioxide, the subsequent growth of biofuel crops such as corn or switch grass sequesters and reduces that carbon dioxide for future fuel production. As such, biofuels offer an ideally carbon neutral renewable energy technology. In addition, replacement of petroleum based commodity chemicals with biomass is crucial for sustainable economy. Expanding the biofuel industry from corn ethanol (10% of today’s gasoline by volume) requires new chemical and engineering technologies to process cellulosic biomass, a readily available and cheap feedstock. Collaborative research in chemical theory in the Auerbach group [1,2], and in chemical engineering practice in the Fan group [3], is paving the way for developing highly efficient catalytic chemical conversion processes to produce chemicals and fuels.

In a biorefinery, biomass can be depolymerized into C5 and C6 sugars by hydrolysis-based approaches. However, to make gasoline-, diesel-, and jet-fuel-range alkanes that are between C8 to C15, C–C bond forming reactions must occur. Aldol condensation is one key C–C bond forming reaction that can be catalyzed by Brønsted and Lewis acid and base catalysts. Zeolite catalysts with tunable pore structures and acidities have shown promise in liquid-phase aldol condensation between biomass-derived furfural and acetone (see Fig. 1). However, catalyst deactivation from reactive oxygenated species and low selectivities to desired products require fundamental understanding of the catalytic reaction pathways within zeolite catalysts, using both computational and experimental methods, which will dramatically push forward the frontiers of biofuel production. In this collaborative project, students will model and measure reaction kinetics of aldol condensation over Brønsted (e.g., Al-MFI) and Lewis acid zeolite catalysts (e.g., Sn-MFI).

Fig 1. Zeolite nanopore with adsorbed aromatic species.

  • Catalyst synthesis and Kinetic study: An REU student in the Fan group will synthesize Brønsted and Lewis zeolites with controllable properties to obtain experimental parameters describing reaction kinetics of aldol condensation within in these zeolites.
  • Atomic level simulation: An REU student in the Auerbach group will learn the application of quantum chemistry methods to model the structures, host-guest interactions, and reaction pathways that govern zeolite-based aldol chemistry.
  • Collaborative Effort: The two REU students and their research mentors will meet regularly to combine their understandings to provide complete chemical and engineering insights into rational design zeolite catalysts for aldol condensation of biomass derived molecules and the production of diesel and jet fuel range alkanes.

CITED REFERENCES:

  1. J. Jae, G.A. Tompsett, A.J. Foster, K.D. Hammond, S.M. Auerbach, R.F. Lobo and G.W. Huber, “Investigation into the shape selectivity of zeolite catalysts for biomass conversion” J Catal, 2011, 279, 257-268.
  2. V. Agarwal, P.J. Dauenhauer, G.W. Huber and S.M. Auerbach, “Ab initio dynamics of cellulose pyrolysis: nascent decomposition pathways at 327 and 600 °C” J Am Chem Soc, 2012, 134, 14958-14972.
  3. A.R. Teixeira, X.D. Qi, C.C. Chang, W. Fan, W.C. Conner and P.J. Dauenhauer, “On Asymmetric Surface Barriers in MFI Zeolites Revealed by Frequency Response” J Phys Chem C, 2014, 118, 22166-22180.
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