Department of Chemistry, University of Central Florida

Research overview/recruitment seminar

Prof. Gang Chen

Towards Precise Control of Plasmonic Nanomaterials: From Synthetic Chemistry to Self-assembly

Abstract: The diversity of materials in structure and properties originates from the 3D arrangement of atoms through chemical bonds which allows atoms to form either large-scale crystals or small molecules. At the nanoscale, aggregates of nanoparticles (NPs) are expected to have unique properties and applications if they can self-assemble like atoms. So far, many literatures have reported the self-assembly of NPs into periodic structures, called superlattices. However, molecular-like NP assemblies are rarely seen due to the absence of valence on their surfaces. In this talk, I will present our work on how to create colloidal analogues of atoms at nanoscale with valence, namely “artificial atoms”, so as to achieve “molecular-type” self-assemblies at nanoscale through the “direct bonding” between “artificial atoms”. More specifically, my talk will show our recent effort on: (1) synthesize NPs with homogeneity in both size and shape like atoms; (2) convert NPs into “artificial atoms” with chemically distinct surface areas that mimic hybridized atomic orbitals, such as sp, sp², sp³, sp³d, and sp³d²; and (3) realize the molecularization of NPs and their “chemical reactions” to achieve diverse and complex nanostructures. The completion of this work results in: (1) new synthetic approaches and a better understanding of growth mechanism, beneficial to the future customized synthesis of NPs; (2) a better understanding of surface chemistry at nanoscale and developing new surface engineering techniques; (3) enrich the colloidal assembly technique and improve the complexity of colloidal metamaterials. It also provides many exciting opportunities for discovering new applications of nanomaterials in many interdisciplinary research fields.

Prof. Jonathan Caranto

The enzymatic rise and fall of the nitramine N-nitroglycine

There are over 200 N–N bond containing natural products, many of which exhibit intriguing bioactivities. Nitramines (R–N(H)NO₂) are critical explosophores in RDX, a common component of military-grade explosives. These functionalities are also found in bacterial natural products, but their physiological role is unknown. To understand the biological function of nitramines, our lab studies the biosynthesis and biodegradation of these groups.

N-nitroglycine (NNG) is a nitramine with weak antibacterial activity made by Streptomyces noursei. The biosynthesis of the nitramine has been proposed to occur via nitration of glycine, perhaps by a nitric oxide dependent pathway. However, the S. noursei genome lacks the genes necessary for such a pathway. Our ¹⁵N-isotope labelling studies suggest that NNG is produced via N-oxygenation of hydrazinoacetic acid step. Furthermore, a biosynthetic gene cluster analysis suggests that one function of NNG is to act as biosynthon for larger bacterial natural products.

Alternatively, NNG may act as a transferable nitrogen currency. Variovorax sp. strain JS1663 can grow using NNG as its sole carbon and nitrogen source by degrading it to nitrite and glyoxylate. The enzyme responsible for this degradation was found and called NnlA. Our studies show that NnlA is a heme enzyme that degrades NNG to nitrite, glyoxylate, and ammonium, thereby producing 2 assimilable nitrogen sources. Our results in these two projects may point towards several hypothetical functions for NNG.