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JUNE 20 - 23, 2023
Sustainability, the Great Lakes, and Chemistry for the Future
Wednesday Afternoon Session Details
June 21, 2023
S8. Education in Chemistry
D. N. Maxwell, Organizer, Presiding
Salon II
2:00 PM
Identifying the relevance of organic chemistry through writing Students in organic chemistry, a historically difficult subject, often exhibit decreasing motivation through the course of the semesters. Therefore, educators seek ways to support students’ motivation for learning. Appealing to students’ interests in academic settings or demonstrating chemistry’s relevance to their life have been suggested as mechanisms to support self-motivated learning. To support students in making their own connections, we implemented an open-ended writing assignment in an introductory level organic chemistry course where students were tasked with choosing an organic molecule and writing about why they found it important to their life. Utilizing a relevance framework, this study investigates the types of connections that students made with their chosen organic compound on personal, societal, and vocational levels. Through qualitative analysis of the writing assignments and interviews with a subset of students, we found that students were identifying the relevance of a variety of organic molecules throughout various times in their life. Personal relevance, rather than societal or vocational relevance, dictated the choice of many of the students’ molecules. Additionally, the students were motivated to study their molecule as shown by the level of detail provided in their assignments. Our study indicates that incorporating short writing tasks that support students in identifying the relevance of chemistry to their own lives may reinforce their comprehension and appreciation of chemistry as it may support their motivation to learn.
Safron Milne (2), milne066@morris.umn.edu, Solaire Finkenstaedt-Quinn (2), Nicholas Garza (2), Steven C. Zimmerman (1), Ginger V. Szymczak Shultz (2). (1) Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, United States(2) Chemistry, University of Michigan, Ann Arbor, Michigan, United States
2:20 PM
Polymer and organometallic systems thinking activities for second semester organic chemistry Two modules related to polymer and organometallic chemistry have been developed and piloted for second semester organic chemistry lecture courses. The modules focus on incorporating introductory systems thinking concepts using the ideas of green chemistry and the United Nations Sustainable Development Goals (UNSDGs) to help students relate chemistry concepts to real world applications. Each module is broken up into multiple activities which could be incorporated into either a traditional lecture as homework assignments or an active learning classroom as group activities. In addition to the UNSDGs, students are introduced to concepts such as atom economy, E-factor, and solvent intensity. Students are challenged to develop Systems-Orientated Concept Map Extensions (SOCME) to illustrate the relationships between chemical principles and big picture ideas. Summative assessments along with the evaluation of SOCMEs provide insight into student learning outcomes for this project.
Amelia Anderson-Wile (1), a-anderson.4@onu.edu, Sara Madsen (2). (1) Chemistry and Biochemistry, Ohio Northern University Getty College of Arts and Sciences, Ada, Ohio, United States, (2) South Dakota State University, Brookings, South Dakota, United States
2:40 PM
Break
2:50 PM
Eliciting student understanding of the relationship between energy and interactions in the context of effects of solvation in organic reactions by engaging them in causal mechanistic reasoning Causal mechanistic reasoning is a powerful explanatory and predictive tool that involves unpacking behaviors and entities at a scalar level below and connecting the lower-level behaviors back to the target phenomenon. Thus, one way to support students as they make sense of complex, multifaceted phenomena is to help them engage in causal mechanistic reasoning by constructing explanations in the context of formative tasks. We have used evidence centered design to construct a set of scaffolded formative tasks, that are intended to elicit student understanding of how and why a particular solvent would change the rate of a given organic reaction. We have collected written responses from about 250 students enrolled in a transformed organic chemistry curriculum and have conducted think-aloud interviews with a subset of 10 students. We found that students struggled to “keep the thread” of explanation going in our pilot activity for this phenomenon, which requires them to retrieve and coherently connect a long chain of inferences. The relationship between strength of the solvent-solute interaction and energy (and stability and reactivity) was one such causal link that students especially struggled with, but that is integral to many chemical phenomena. Using resources framework as our theory of cognition, we have characterized the resources leveraged by students in their responses, the type of reasoning they used, and the type as well as number of causal linkages established between ideas. Using this data, we were also able to identify areas which are specifically troublesome where they need more scaffolding and/or instructional support. This work can inform us on how to best design curriculum and assessment materials to support students in constructing causal mechanistic explanations to reason through other complex phenomena.
Kriti Seth (1), sethkrit@msu.edu, Elizabeth L. Day (2), Melanie Cooper (1)(3). (1) Chemistry, Michigan State University, East Lansing, Michigan, United States, (2) Chemistry & Biochemistry, The University of Texas at El Paso, El Paso, Texas, United States, (3) CREATE for STEM, Michigan State University, East Lansing, Michigan, United States
3:10 PM
Case study on post-secondary chemistry instructors’ resources for planning instruction This study draws inspiration from mathematics education research that explores how K-12 mathematics teachers develop resources (e.g., in-class problems, homework sets, learning management systems, etc.) as part of their teaching work. This research emphasizes the importance of teachers sharing resources. To understand this work in post-secondary chemistry instruction, we used a case-study approach to examine how three post-secondary instructors with varying levels of experience develop resources for teaching chemistry. We qualitatively analyzed multiple interviews and observations collected over multiple semesters. We capture what resources the instructors adopted, how they were developed over time, and examine the broad resource systems developed for their work. We will present how the three instructors developed resources for their contexts and what contextual factors, especially their social interactions, influence their work, providing an alternative perspective to understanding post-secondary chemistry instruction.
Rebecca Fantone, rfantone@umich.edu, Ginger V. Szymczak Shultz. University of Michigan, Ann Arbor, Michigan, United States
3:30 PM
Analysis of silylated polyphenols found in banana peels Polyhenols have been found to have beneficial properties of interest to human health. They have been detected in a large variey vegetable sources. Banana peels, which are a usually discarded by-product of banana foods processing, are an important source of polyphenols. That enhances their value as a potential source of medically valuable substances. Polyphenols from banana peels have been studied by chemical and spectroscopic methods such as HPLC-UV and HPLC-MS. Their study by GCMS is limited by the fact that their boiling points are beyond the ranges of the instruments. Transformation of the polyphenols to derivatives with lower boiling points is one way to overcome that challenge. In this study, banana peels were extracted and derivatized by silylation and the derivatives were studied by GCMS. The results will be presented at the CERM.
Barry Miburo, bmiburo1@gmail.com. Sciences and Mathematics, Abraham Baldwin Agricultural College, Tifton, Georgia, United States
3:50 PM
Break
4:00 PM
Investigating how organic chemistry faculty structure their knowledge and their beliefs about student learning Previous literature on how people learn suggest that disciplinary experts organize their knowledge differently than the beginners. Studies from a wide range of fields such as physics, computer science, and chess show that experts in a discipline tend to organize their knowledge around overarching ideas which help them access and use that knowledge in new contexts, whereas beginning students tend to focus on disconnected surface features. In chemistry, such studies have been limited to reaction card sorting tasks and to our knowledge there are no investigations on how organic chemistry faculty structure their knowledge as a whole. In this study, in a semi-structed interview setting, we explore how organic chemistry faculty (n=8) structure their knowledge and faculty beliefs about student learning using a Grounded Theory approach to analyze interview data. Initial themes that emerged from interviews suggest faculty tend to organize their knowledge around overarching ideas such as structure and properties relationships, energy and bonding and interactions. Furthermore, these themes tend not to align with the ideas faculty believe are important for students to learn. We propose that findings from this study can expand the literature base on how organic chemistry experts structure their knowledge as well as how faculty may support students to think and organize knowledge. Additionally, by explicitly eliciting the disconnect between faculty knowledge structures and how teaching and learning are enacted in their courses, it may be possible develop faculty support structures that help them better align these their beliefs with what we know about the development of expertise.
Sewwandi Abeywardana, abeyward@msu.edu, Melanie Cooper. Chemistry, Michigan State University, East Lansing, Michigan, United States
4:20 PM
Analysis of the ashes of the peels of bananas grown in South Georgia The peels of bananas grown in South Georgia were incinerated and extracted with water. The soluble bases contained in the ashes were titrated with hydrochloric acid. The extracts that were found to contain hydroxides were treated with barium chloride to precipitate the carbonates and the hydroxides were titrated separately. The elements contained in the extracts, the extraction residues and the total ashes were analyzed by ICP atomic absorption spectroscopy. The results will be presented in the 2023 CERM.
Barry Miburo, bmiburo1@gmail.com. Sciences and Mathematics, Abraham Baldwin Agricultural College, Tifton, Georgia, United States
S11. Organic
D. B. Lawson, Organizer, Presiding
Salon III
2:00 PM
Riboflavin binding protein: Vitamin interactions in the binding pocket Riboflavin, a B family vitamin that is characterized by an isoalloxazine ring connected to a ribityl moiety via a C-N bond, is the precursor of two coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These two cofactors are involved in many electron and proton transfer reactions, DNA repair, protein folding, fatty acid and amino acid oxidation, and other metabolic processes. Humans have lost the ability to synthesize riboflavin which is provided through diet and transported in cells by carrier proteins. Recently, Riboflavin receptors have been reported as overexpressed in several types of cancer. Thus, the nature and specificity of the vitamin-carrier protein interactions are critical. We have synthesized and characterized a series of Riboflavin derivatives selectively modified in the ribityl region to address the structure-activity relationships. The individual and combined effects of these structural modifications on protein binding of the derivatives have been examined through fluorescence studies.
Simona Marincean, simonam@umich.edu, Diana Nichols, Marilee Benore. Department of Natural Sciences, University of Michigan - Dearborn, Dearborn, Michigan, United States
2:20 PM
Reliable C-3 substitution in pentadiynyl Nicholas reactions and the preparation of dichlorodimethoxy analogues of hinokiresinol and nyasol The application of pentadienyl cations and their pentadienylmetal and pentenylmetal equivalents towards skipped diene synthesis is a challenge, due to the dominance of C-1 over C-3 nucleophilic attack. The reaction of the pentadiynyldicobalt cation complexes with nucleophiles feature the dominance of their C-3 reactivity, and they will be discussed, along with the scope of their nucleophilic partners and limits in their regioselection. The application of these reactions in the synthesis of both (Z)- and (E)- isomers of antimalarial hinokiresinol/nyasol analogue also will be presented.
Brent St. Onge, stongeb@uwindsor.ca, Marcus Muresan, James R. Green. Chemistry, University of Windsor, Windsor, Ontario, Canada
2:40 PM
Break
2:55 PM
New developments in visible light-mediated aza Paternò-Büchi reactions Azetidines are four-membered nitrogen-containing heterocycles that represent powerful synthetic building blocks in the design of bioactive molecules. The azetidine system is most-commonly accessed via intramolecular nucleophilic substitution or by the reduction of beta-lactams, but these methods are limited in scope. A [2+2]-cycloaddition between an imine and alkene, referred to as the aza Paternò-Büchi reaction, is arguably a more direct and efficient transformation to access azetidines. We have recently developed a new design principle for aza Paternò-Büchi reactions relying on the activation of activated alkenes or functionalized imines with a suitable photosensitizer and visible light. We herein report new developments in this class of transformations that overcome existing limitations in inter- and intramolecular [2+2]-cycloadditions to give rise to previously inaccessible azetidines in a single synthetic transformation.
Seren Parikh, sgparikh@umich.edu. University of Michigan, Ann Arbor, Michigan, United States
3:15 PM
Photo and catalytic desulfurizations: Application to organic molecules, peptides and proteins A high yielding photodesulfurization of cysteine containing peptides reported with minimum equivalents use of the phosphine reagents. This facile desulfurization method doesn’t demand the use of radical initiator or photocatalyst or exogenous thiols or other H-atom donors. It has wide applicability in organic and aqueous solvent conditions. This method was successfully examined with unprotected and protected peptides with different combinations of amino acids. The applicability of this method was implemented with synthesis of polypeptides and proteins. In addition, a catalytic thiyl-radical mediated desulfurization method was developed, and this method utilizes a catalytic phosphite reagent and thermal initiator with stoichiometric silane as a hydrogen donor. This method was applicable to organic molecules and small peptides.
Venneti Naresh Murty, nareshmurty@gmail.com, Ganesh Samala, Rana Morsy, Lawrence Mendoza, Jennifer L. Stockdill. Chemistry, Wayne State University, Detroit, Michigan, United States
3:35 PM
Investigating coupling reagents for the synthesis of ferrocene hybrids from ferrocenecarboxylic acid in organic laboratories Synthesis of ferrocene hybrids for anti-cancer studies in primarily undergraduate institutions has been challenging due to the limited availability of starting materials and the lack of stability of recommended synthetic pathways. This project is focused on exploring multiple synthetic pathways of a selection of ferrocene hybrides with ferrocenecarboxylic acid and a set of anilines with various substituents. A combination of coupling reagents such as dicyclohexyl carbodiimide (DCC) with hydroxy-benzotriazole (HO-Bt) were investigated for these syntheses under atmospheric conditions. The work was designed for an undergraduate organic chemistry laboratory series and modifications were implemented through multiple sections to evaluate potential combinations for each of the anilines used for these studies. This presentation will address the synthetic approach, challenges, and product yields for various coupling combinations.
Marwa Abdel Latif (1), abdellmk@udmercy.edu, Steven Scribner (1)(2), scribnsl@udmercy.edu, Mara Livezey (1), livezemr@udmercy.edu, Eleni Geragosian (1), geragoek@udmercy.edu. (1) University of Detroit Mercy, Detroit, Michigan, United States, (2) University of Michigan Dearborn Office of Metropolitan Impact, Dearborn, Michigan, United States
S7. DEI Initiatives Including Social Media Usage in Industry and Academia: TikTok and Tweet Your Way to a Diverse Workforce
S. P. Hickey, Organizer, Presiding
Salon V
2:00 PM
Introductory Remarks
2:05 PM
Chemists with disabilities and inclusion: ACS efforts and resources The American Chemical Society has been working to include people with disabilities into the chemical enterprise for many years. A brief history of these efforts will be described, followed by a discussion of the resources currently available to the chemistry community as a whole with reference to issues concerning the education and employment of individuals with disabilities.
Jim Landis, jlandis@home.msen.com. Detroit Local Section, American Chemical Society, Detroit, Michigan, United States
2:30 PM
Investing in the bigger picture: Importance of incorporating diversity, equity, and inclusion into research As scientists, we often address questions from a bottom-up or top-down approach. Whichever way you attack questions or challenges in science, the bigger picture is always in view. We can approach diversity, equity, and inclusion in research (DEIR) efforts in this way too. When we invest in improving DEIR, we see positive results at the local level (student/trainee, department, institution) and in the broader community (chemistry, the scientific field, and outside of the scientific world). In this talk, we will discuss what makes up a valuable investment in DEIR, and how you and your department can work towards making this investment. Then we will talk about the overall potential outcomes of making this investment and how everyone wins when DEIR is a conscious and active component of the field.
Brianna Simms, briana.simms@duke.edu. Departments of Chemistry, University of Cincinnati, Cincinnati, Ohio, United States
2:55 PM
Break
3:05 PM
Understanding diversity, equity, and inclusion in chemistry through National Diversity Equity Workshops (NDEWs) The culture in every discipline exhibits important differences emerging from the differentiated modalities required to practice and advance a given discipline and its ontological development. Thus, it is critical to characterize and analyze how multiple systems intersect to produce inequalities within a discipline over a period. Our project ‘Open Chemistry Collaborative in Diversity Equity (OXIDE)’ by organizing biennial workshops- National Diversity Equity Workshops (NDEWs) tries to articulate and contextualize solutions regarding DEIR driven by the top-down hypothesis where we argue that holding department chairs accountable and providing them with appropriate tools will lead to DEIR. The National Diversity Equity Workshops represents is a biennial series of diversity workshops designed for chairs of leading research intensive (RI) chemistry departments to discuss methods and policies in order to reduce inequities that have historically led to disproportionate diversity representation on academic chemistry faculties by helping to change the infrastructure from the top down. The findings have been analyzed and reinterpreted contextually in order to understand how people learn the concepts, practices, and ways of thinking within chemistry departments and a significant portion of the faculty have been driven to advance these efforts either because of social justice or the business case.
Vartike Chandra Saman, vsaman1@jhu.edu. Departments of Chemistry, Johns Hopkins University, Baltimore, Maryland, United States
3:30 PM
Fostering diversity, equity, inclusion, and respect across the chemistry enterprise The talk will highlight the work being done by the Committee on Minority Affairs (CMA), American Chemical Society (ACS) to engage and promote Diversity, Equity, Inclusion and Respect across the chemical enterprise. The Committee on Minority Affairs was established in 1993 by the American Chemical Society to address the racial and ethnic underrepresentation in ACS membership. Learn how CMA approaches this opportunity through our mission, vision and strategic goals developed to help accomplish inclusivity and respect within the chemistry enterprise.
Reni Joseph, rjoseph15@stlcc.edu. Departments of Chemistry, St. Louis Community College, St. Louis, Missouri, United States
S9. f-Block Extravaganza: The Best Symposium at CERM
M. Rashid, S. White, Organizers, Presiding
Salon VI
2:00 PM
f-Block elements and the environment: A blessing and a curse Over the past 75 years, there has been a growing global dependence on the elements in the lanthanide and actinide series for many critical uses. This talk will cover the benefits and challenges of f-block elements and the environment including the main uses of f-block elements, extraction/recovery, applications, and wastes produced during processing and at end-of-life disposal. Commercial sources of lanthanides include ion exchange clays and bastnaesite, monazite, and xenotime minerals; however, the extraction and recovery process is challenging and resource intensive. An underlying theme of this talk will be on the “blessing and curse” of the f-block. Although lanthanides are used in many clean energy technologies such as powerful magnets for wind turbines and electric car motors, their sourcing and processing is energy intensive and uses large amounts of fossil fuel to produce. Similarly, uranium is used to produce low carbon electricity; however, disposal of spent nuclear fuel remains a global challenge. Separating lanthanides and actinides is particularly challenging and has been the subject of extensive research. The talk will also discuss the potential benefits and challenges of sourcing f-block elements from unconventional materials such as coal combustion products (fly ash), phosphate rock, and electronic waste.
Timothy Dittrich, timothy.dittrich@wayne.edu. Civil & Environmental Engineering, Wayne State University, Detroit, Michigan, United States
2:25 PM
Employing radicals and bismuth in lanthanide single-molecule magnet design Molecules that possess an energy barrier to spin inversion have intriguing potential applications in areas such as magnetic refrigeration, molecular spintronics and high-density information storage. For these applications, however, key performance characteristics such as large spin-relaxation barriers (Ueff) and high magnetic blocking temperatures (TB) are required. Lanthanides have been proven to be particularly well-suited for the design of single-molecule magnets owing to their large magnetic moments and magnetic anisotropy that stem from strong spin-orbit coupling of the 4f orbitals. By using lanthanide ions such as Tb3+, Dy3+, and Er3+ which possess intrinsically large orbital angular momentum, significantly higher Ueff and TB can be achieved. A general methodology to improve TB in multinuclear single-molecule magnets is to generate strong magnetic exchange between lanthanide centers through the employment of radical bridging ligands with diffuse spin orbitals that can penetrate the core electron density of the lanthanide ions where the 4f spin orbitals lie buried. Another successful approach to strong coupling targets the use of heavy p-block elements since their diffuse valence orbitals facilitate better penetration of the core electron density of the lanthanide ions relative to diamagnetic ligands comprising lighter p-block elements. Here, we will present the synthesis of multiple lanthanide single-molecule magnets that contain radical ligands and bismuth clusters, respectively.
Selvan Demir, sdemir@chemistry.msu.edu. Departments of Chemistry, Michigan State University, East Lansing, Michigan, United States
2:50 PM
Cadmium Schiff base complexes that glow: Unexpected structures and room temp phosphorescence Exploratory work with respect to the title complexes has been surprising and exciting. We will present our structural findings by an analysis of single crystal X-ray and other spectroscopic techniques. These complexes have Ci symmetry and remarkable room temperature phosphorescence with lifetimes on the millisecond scale. Synthesis, structural characterization, and photophyscial characterization will be discussed for these fascinating cadmium schiff base complexes.
Morgan Deal (1), Matthias Zeller (2), Evan R. Trivedi (1), trivedi@oakland.edu. (1) Oakland University, Rochester, Michigan, United States, (2) Purdue University, West Lafayette, Indiana, United States
3:15 PM
Break
3:25 PM
Coordination chemistry studies for ion flotation to selectively remove nickel(II) and cobalt(III) using amine-based ligands Ion flotation is a surfactant-based separation process used to concentrate metal ions present in dilute aqueous solutions using surfactants with an opposite charge to that of the metal ion. Due to the emerging electric vehicle (EV) industry and plans to reduce carbon emissions by fuel operated vehicles, nickel, and cobalt have found an increased demand in manufacture of EV batteries. In this research we propose extracting nickel and cobalt from fly ash a byproduct of coal mining rich in 3d and 4d metals using ion flotation providing an alternative source to the fast-depleting natural reserves present. Ligand field theory and coordination chemistry gives insight to the preferred geometries of these metal complexes; cobalt (III) d6 low spin is octahedral geometry and nickel (II) d8 low spin is square planar geometry. We hypothesize that we can have selective removal of cobalt and nickel by using strong field ligands that promote these geometries. In this research we will use sodium dodecyl sulfate as the anionic collector surfactant and sequestriant ligands are: triethylenetetramine, ethylenediamine, cyclen, 1,2-Bis(3-aminopropylamino) ethane (3,2,3) and N,N′-Bis(3-aminopropyl)-1,3-propanediamine (3,3,3). The parameters to be studied include molar ratio of coordination complexes of ligand to metal, optimum concentrations of surfactant and the pH. They will be studied using coordination chemistry experiments with subsequent analysis using UV-visible followed up by TD-DFT calculations, mass spectrometry and ICP-MS. Data obtained shows highest amount of nickel removal occurs at basic pH with ethylenediamine and triethylenetetramine showing 98% nickel recovery. In a mixture of gadolinium and nickel using 333 and 323 selective recoveries for nickel occurred at pH 11 with 99% recovery and gadolinium at pH 8 at with 80% recovery. Coordination chemistry studies and a preliminary crystal structure shows nickel coordinates in 2:3, 1:3 with triethylenetetramine, ethylenediamine respectively suggesting an octahedral structure of the complexes.
Eva Mwakazi, evamwakazi@wayne.edu. Chemistry, Wayne State University College of Liberal Arts and Sciences, Detroit, Michigan, United States
3:50 PM
Multi-electron redox chemistry with thorium(IV) iminoquinone complexes Thorium complexes primarily exist in the thermodynamically stable (IV) oxidation state, with limited examples of low-valent thorium(III) complexes known. As a result, redox chemistry with thorium is challenging without carefully designed ligand environments. This redox-restricted nature of thorium(IV) makes redox-active ligands an attractive option to facilitate multi-electron redox chemistry. In this work, a series of thorium(IV) complexes featuring the redox-active iminoquinone ligand and its derivatives, including the iminosemiquinone and amidophenolate species, were synthesized and isolated. Oxidation chemistry resulted in formation of a terminal oxo species, which is rare for thorium species. Spectroscopic and structural characterization of each derivative established the +4 oxidation state for thorium with redox chemistry occurring on the ligand. Magnetic and EPR studies confirmed the formation of new thorium species featuring multiple ligand radicals as well.
Suzanne C. Bart, sbart@purdue.edu. Department of Chemistry, Purdue University System, West Lafayette, Indiana, United States
S10. Materials and Surface Chemistry
D. B. Lawson, Organizer, Presiding
Salon VII
2:00 PM
Electropolymerization of organometallic cyclopentadienyl pyridazines for advanced electronics Heterocycles and their derivatives have been of great interest in organic electronic applications, such as organic light-emitting diodes, (OLEDs) and organic photovoltaics (OPVs). Here we report the formation of a cyclopentadienyl pyridazine organometallic complex that incorporates metal atoms directly into a thin-film electropolymer. Electropolymerization allows for convenient pathways for tuning band structure, as well as other chemical and physical properties. The electrochemical properties and structural characterization will be discussed, as well as insights into the mechanism of polymerization.
Valeria Mattern Mondragon (1), Daniel J. Little (1), danlittle1010@hotmail.com, Nathan C. Tice (2), Seth T. King (3). (1) Mathematics, Computer, and Natural Sciences, Ohio Dominican University, Columbus, Ohio, United States, (2) Department of Physical Sciences, University of Findlay, Findlay, Ohio, United States, (3) Department of Physics, University of Wisconsin-La Crosse, La Crosse, Wisconsin, United States
2:20 PM
Morphology-controlled vapor-phase nanowire growth with Ruddlesden-Popper Lead Bromide Perovskite Two-dimensional (2D) Ruddlesden-Popper (RP) halide perovskite has attracted significant attention as a promising candidate for high-efficiency light sources. RP perovskites, when synthesized into well-defined nanowires (NW), have the potential to serve as nanoscale coherent light sources by incorporating optical cavity effects with their light emission behaviors. However, RP perovskites tend to grow in macroscopic thin sheets as opposed to relevant NW structures due to the layered nature of the crystal lattice, which necessitates a new way of controlling nanoscale morphologies. Here, we achieve NWs of RP BA2PbBr4 (BA= butylammonium), for the first time, using chemical vapor deposition (CVD) by systematically navigating a wide range of growth conditions and constructing growth regimes of distinct morphologies. Of the two particular regimes that produce well-formed nanostructures, we find that RP BA2PbBr4 grows into energetically-favored thin nanoplatelets (NPLs) at high temperatures whereas intermediate temperatures allow it to first grow into 3D pyramidal nuclei and then get elongated into NWs upon continued growth. We propose temperature-dependent diffusion of surface species as a deciding factor of our morphological control. We present crystallographic and elemental analyses to confirm that our NWs have appropriate lattice structures and chemical stoichiometry of BA2PbBr4. Static and time-resolved optical measurements show quantized absorption and emission features at 400 and 406 nm, respectively, with a radiative decay time of 1.7 ns which is much quicker than the 8.7 ns decay time of prototypical 3D CsPbBr3 perovskite. The RP NWs exhibit a strong exciton binding energy of 276 meV, which can be understood by the reduced dimensionality of BA2PbBr4. The strong absorption and radiative emission characteristics suggest that the RP BA2PbBr4 NWs are good candidates as bright, ultrasmall light sources for nanophotonic and optical communication applications.
Pushpender Yadav, yadavpus@msu.edu, Kyeongdeuk Moon, Anupam Biswas, Seokhyoung Kim. Chemistry, Michigan State University, East Lansing, Michigan, United States
2:40 PM
Ultrafast excited-state interactions between carbon dots and luminescent materials Carbon-based-nanoarchitectures have been in the forefront of research for last three decades with applications in interdisciplinary areas of science and engineering. In recent years, a new class of Carbon-nanoarchitectures have emerged called Carbon dots with absorption in the UV to visible region and variable photoluminescence. Electrostatic-interaction or covalent-binding of organic-chromophores or semiconductor-nanomaterials to Carbon Dots can be achieved to develop hybrid optical-materials with interfacial-energy/charge-transfer interactions. In this study, we have designed and developed a novel photoactive-nanomaterial obtained by the spontaneous electrostatic coupling of negatively charged carbon nanodots (multi-colored N-doped and without-doped) with a dye, 3,3′-dihexyloxacarbocyanine iodide(DiOC6). We have also probed the interaction between different bandgap perovskites with the carbon dots. Using steady-state, time-resolved absorption, and photoluminescence experiments, we have investigated the excited-state-interactions in the CD-/dye and CD-/perovskites hybrid assembly. PL studies revealed enhancement of the dye emission (75% to 122%) upon addition of CD- (without vs doped), which supports the fact, there is an electrostatic and hydrophobic-interaction which causes the enhancement. On the other hand, PL studies shows quenching of perovskites emission upon addition of CD-. Ultrafast transient absorption measurements confirmed there are two different processes going on in two hybrid systems. The PL enhancement in CD-/dye is because of the reduced non-radiative deactivation due to energy-transfer from CD- to dye, achieved by coupling DiOC6 and Carbon dots, produced a long-lived species. On the other hand, CD-/perovskites showed interfacial-charge-transfer process.
Sukanya Saha, sukanya.saha@wmich.edu. Chemistry, Western Michigan University, Kalamazoo, Michigan, United States
3:00 PM
Break
3:15 PM
CdS ultrasmall quantum dots: Synthesis and gelation kinetics The generation of environmentally friendly fuels like H2 from renewable energy sources is a critical component of efforts to combat the energy crisis and climate change. CdS is a visible light-absorbing semiconductor often used for photocatalytic water splitting to generate H2 gas. Using CdS quantum dots (QDs), materials with 0D dimensionality, have benefits over bulk materials such as increased surface area and light absorption, in addition to the ability to tune the light absorption wavelength by controlling quantum dots’ size. However, QDs tend to aggregate with time, decreasing their efficiency. Forming QD assemblies prevents their aggregation, and our group already showed that the oxidative assembly of QDs into aerogels (AGs) improves their photocatalytic efficiency by enabling multiple photogenerated electrons to be driven towards catalytic sites, besides keeping high surface areas. To obtain a better comprehension of the energy transfer processes involved in the photocatalytic application of CdS QDs and AGs, better computational models are needed to more precisely calculated the band energies and overall electronic structure of the materials, especially concerning interparticle bonding. The development of more advanced models is hindered not only by the lack of data regarding CdS QDs band energies, but also by the lack of good and reproducible synthesis protocols for CdS QDs with sizes below 2.0 nm. The synthesis of these ultrasmall quantum dots with precise size control is a challenging task, and can be considered the bottleneck for the further modeling strategy that starts with smaller QDs sizes, going to bigger sizes and then to the aerogel frameworks. Herein, we will demonstrate a controlled synthesis method for CdS quantum dots ranging in diameter from 1.5-3.2 nm, and their oxidative assembly to from gels, and aerogels. Finally, we will provide spectroscopic data for the CdS ultrasmall quantum dots and discuss our goals for the future characterization of the QDs and AGs with respect to electronic structure and computational modeling.
Isa Ahmed, isaahmed41@gmail.com, Vinicius Alevato Neves, Stephanie L. Brock. Chemistry, Wayne State University College of Liberal Arts and Sciences, Detroit, Michigan, United States
3:35 PM
Photoluminescence enhancement of quantum-sized gold nanoclusters by Chemiluminescence-resonance-energy-transfer Over the past few decades, quantum-sized gold clusters have emerged as ultra-small nanomaterials with intriguing photophysical characteristics such as good photostability, long-luminescent lifetimes, and large two-photon cross sections. This has paved the way for their applications including bio-imaging, energy harvesting, and optical sensing. However, their relatively low Photoluminescence Quantum Yield (PLQY) when compared to organic dyes, quantum dots, and luminescent polymers is limiting their use. The all-chromophore conjugation of clusters is one promising strategy leading to manifold PL enhancement in clusters. However, the greater extent of conjugation leading to chromophore aggregation is one drawback of this strategy. One lesser-utilized strategy for PL enhancement in clusters is by energy transfer from a covalently bonded chemiluminescent (CL) Reagent to the gold cluster. The CL reagent acts as a donor and generates a high-energy state leading to energy release after the reaction. This photonic energy can be accepted by the conjugated cluster like other ‘signal-on’ acceptors such as fluorescent dyes, polymers, and quantum dots. The main objective of this study is to enhance PLQY in gold clusters by the avenue of resonance energy transfer by a CL reagent, N- (4-aminobutyl)-N-ethylisoluminol (ABEI). The clusters Au25(SG)18-, Au22(SG)18, and Au18(SG)14 are synthesized by altering the ratios of Au with Glutathione and NaBH4 under different reaction conditions. The ABEI-conjugated clusters are synthesized by known EDC/NHS coupling reaction. The covalently bonded cluster with ABEI is probed for photoluminescence enhancement by the CRET mechanism. The effect of non-covalent interactions between ABEI and clusters is also utilized for enhanced PL in gold clusters. The CL intensity of ABEI is also probed for enhancement upon binding with clusters. 1H NMR and ESI-MS revealed the number of ABEI conjugated to the clusters. The CL and PL counts are observed in the microplate reader. The CL-spectra profile of ABEI and ABEI-Cluster system along with PL curves confirmed the energy-transfer events.