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Research

Thank you for your interest in The Rosenzweig Group. Research in our lab focuses on synthesis, stability, and toxicity of semiconductor nanoparticles, with the overall goal of increasing safety and sustainability. There are many uses for semiconductor nanoparticles including biomedical imaging, biosensors, and photovoltaics. Our lab is researching the sustainability, functionality, and environmental impact of these particles. Current projects in our lab involve synthesizing nanomaterials with unique luminescent properties that can be used in optical coding applications, and testing their toxicity in zebrafish models. Our lab is also working to replace currently used toxic and rare nanomaterials with benign and earth abundant nanomaterials to minimize adverse effects on human health and the environment, while reducing the cost of nanotechnology applications.

Research Supported By NSF Award CHE-1506995

Non Toxic InP Quantum Dots for Luminescence Cellular Imaging and Sensing

ABSTRACT

Luminescent semiconductor nanoparticles are materials with an extremely small diameter, about 10,000 times smaller than the diameter of a single human hair. Their small size gives them unique optical properties. When irradiated, they emit intense visible light in a color that depends on their size, shape and composition, making it possible to generate a rainbow of visible emission colors from a single semiconductor material. Luminescent semiconductor nanoparticles have found use in recent years in biomedical imaging and sensing applications, in light emitting devices including cell phone screens and flat screen TVs, and in energy converting photovoltaic devices. Their distribution across a wide range of economic sectors has raised serious health and environmental concerns since these nanomaterials often contain cadmium, a highly toxic substance. Zeev Rosenzweig, at UMBC is developing novel synthesis, and surface modification methods to prepare a new generation of cadmium-free, and therefore non-toxic luminescent semiconductor nanoparticles made of indium phosphide (InP). Rosenzweig and his students also demonstrate the utility of InP nanoparticles as cellular imaging agents to study how enzymes work in living cells. Dr. Rosenzweig is active in the recruitment of underrepresented minorities into STEM fields by partnering with the Interdisciplinary Consortium for Research and Educational Access in Science and Engineering (INCREASE). He also works with veterans to give them research experience and to contribute to their professional development.

Research Supported by the Center for Sustainable Nanotechnology NSF Award CHE-1503408

ABSTRACT

The Center for Sustainable Nanotechnology (CSN) enables fundamental studies of the specific molecular interactions expected to occur when the surfaces of engineered nanoparticles come into contact with biological interfaces and components. The chemical insight gained from molecular and mechanistic studies of nano-bio interactions is used to intentionally design nanomaterials that provide the desired technical functions while also minimizing potentially adverse consequences with the environment. CSN research leads to introduction of a new generation of safer nanomaterials that may impact multiple sectors of the economy including energy, transportation, electronics, food, and agriculture. The CSN prepares a new generation of scientific innovators by providing education and professional development opportunities focused on innovation, communication, leadership, and interdisciplinary scientific skills. CSN researchers actively encourage diversity within chemistry through CSN-run workshops on overcoming implicit bias, recruitment of graduate students and postdocs, and Center-sponsored research experiences for students and faculty from underrepresented groups as well as veteran undergraduates. CSN researchers encourage diversity in public engagement, develops and practices informal communication skills, and expands the highly successful sustainable-nano.com blog to include Spanish language content, K-12 activity materials, podcasts, and videos.

CSN integrates experiments with computation in three integrated research focus areas (RFAs). RFA1 develops new materials with precisely controlled structure and properties, molecular-level characterization tools such as advanced non-linear optical methods and sub-diffraction imaging, and novel computational methods spanning length scales from nanometers to millimeters. RFA2 uses the RFA1 tool kit to understand, control, and predict how nanomaterials attach to, penetrate, and alter cell surfaces using lipid bilayers as model systems for cell membranes. RFA3 determines the molecular processes by which pristine and environmentally transformed nanomaterials interact with living systems with diverse cellular chemistries, ranging from single cell to multi-cellular organisms. The integration of these three RFAs enables the Center to establish how nanomaterial properties and behavior impact biological outcomes. This knowledge leads to reliable predictions of biological responses to existing and future nanomaterials and guides the design and synthesis of safe, sustainable nanomaterials. In pursuing the project goals, the CSN puts particular emphasis on the synthesis, characterization, and molecular-level interactions initiated by complex, composite nanomaterials that are being used in emerging and future nano-enabled commercial technologies.

Current Projects:

Fluorescence Lifetime Spectroscopy of Quantum Dots:

Core-shell, semiconductor quantum dots (QD) have been used extensively as an alternative to molecular fluorophores in biological assays.  Most recently, QD have been included in many consumer electronic devices, photoelectronics and The synthesis methods to form core-shell QD are well established; however, they still often lead to inconsistencies in QD structure and properties. To date, steady-state fluorescence spectroscopy, UV-VIS absorbance spectroscopy, and transmission electron microscopy are the standard methods employed for the characterization and determination of the overall quality of luminescent QDs. In our lab we are employing time-correlated single photon counting based fluorescence lifetime spectroscopy to provide valuable, real time information about QD core-shell structures as they form, and and degrade in varying condition relevant to biological systems.

Minimizing or preventing QD degradation is very important because QD toxicity is often attributed to degradation products like cadmium ions. Using fluorescence lifetime spectroscopy to monitor the formation and degradation of QD in real time will enable us to synthesize QDs that are more stable in biological systems and in the environment.

Dr. Taeyjuana Curry

Synthesis and Characterization of ZnSe/ZnS Quantum Dots

Current work in the group involves the synthesis and characterization of luminescent ZnSe/ZnS QD. The immediate objective is to compare the ZnSe/ZnS system to the traditional CdSe/ZnS system. ZnSe/ZnS QD are attractive because they are cadmium-free, made from earth abundant elements, and they can emit light with wavelengths ranging from UV to visible.  It is anticipated that ZnSe/ZnS QD may eventually replace CdSe/ZnS quantum dots in some applications, so the next objective will be to study any environmental impact these QD may have. Ultimately, we intend to study QD interactions with biological systems and organisms- such as nematodes, daphnia, shewanella, and zebrafish. And finally, we hope to investigate possible applications of these ZnSe/ZnS QD, including the possibility of applying them in photocatalytic cells.

Denise Williams

Reducing Toxicity of CdSe/ZnS Quantum Dots

One project in our group focuses on reducing the toxicity of ZnSe/ZnS QD. We are currently capping cadmium selenide, zinc sulfide core/shell QD with various molecular ligands that are synthesized within the group or that are bought. These ligands covalently bind to the zinc sulfide shells of QD through thiol chemistry. These ligands differ by the number of thiol bonds they can create with the zinc sulfide shell. 11-mercaptoundecanoic acid, the store bought ligand, is a monodentate ligand meaning it forms one thiold bond. The ligands synthesized by by the group all contain di-hydrolipoic acid, which can from two thiol bonds with the shell.  Using these ligands, we are studying the role surface chemistry plays on QD colloidal stability in solutions of increasing complexity. In addition to studying QD stability, we are analyzing QD toxicity in the developing zebrafish embryo. Specifically, we are studying how the toxicity of QD differs according to the surface chemistry.

Melissa Muth

Ligand Effect on Quantum Dot Stability

Ligand Effect on Quantum Dot Stability: We are developing an advanced ligand technology to significantly improve the stability of luminescent QD in biological solutions. We have prepared a series of bi-thiolated ligands that contain varying polyethylene glycol (PEG) moieties in their structure. Bi-thiolated ligands utilize two sulfur coordinating groups to complex with QD as opposed to mono-thiolated ligands. Because bi-thiolated ligands are more strongly coordinated to the QD, there is an expected increase in stability of these QD in biological solutions. We are currently capping both InP/ZnS and CdSe/ZnS QD with these ligands, intending to show InP QD as a non-toxic alternative to CdSe QD. The effects of QD stability will be tested on an embryonic zebrafish model to determine the relationship between QD stability and toxic effects.

Richard Brown