Mamun Sarker
I identify as a molecular architect. My building blocks are not bricks and mortar but specifically designed small organic molecules based on carbon atoms and chemical bonds. I construct atomically precise planar carbon nanomaterials, including zero-dimensional graphene quantum dots or nanographenes (NGs), one-dimensional narrow strips of graphene called graphene nanoribbons (GNRs), and two-dimensional graphene sheets containing nanoscopic periodic holes known as nanoporous graphenes (NPGs). These carbon nanomaterials are a unique form of graphene fabricated from specifically crafted functional organic molecules, macrocycles, and polymers using a well-established bottom-up synthesis method. My doctoral and postdoctoral work has been focused on engineering these materials at the molecular level, tailoring their properties for specific applications. The following highlights my career summary:
10+ years leading independent and collaborative materials research expertise, including conducting solid state and wet experiments, method development, rigorous data analysis, interpretation, and innovative method development showcased by 9+ co-authored publications and 5+ first-authored manuscripts under review/preparations.
Research acumen and fast-paced dynamic research proficiency with an ability to design, conduct, and interpret STM experiments under ultra-high vacuum (UHV) on coinage metal surfaces, as demonstrated by developing 5+ optimized STM methods and SOPs for carbon-based semiconducting materials
7+ years of expertise in the design, synthesis, purification, and characterization of small organic molecules/ polymers for the bottom-up solution and STM-enabled on-surface fabrication of atomically precise planar carbon nanomaterials focused on synthetic electronics, evidenced by creating 20+ new carbon-based semiconducting and quantum materials, 5+ modular and selective synthetic approaches
I am open to new research roles in industrial, national labs, or academic settings. I welcome prospects connected to materials research and characterization encompassing Quantum Materials, Semiconductors, Surface Science, Biomedical, and Pharmaceutical research.
Please don't hesitate to reach out to me, and I look forward to engaging in conversation/chat!
Email: msarker39@huskers.unl.edu
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University of Nebraska-Lincoln
University of Dhaka
Mamun Sarker of Gazipur earns University of Nebraska-Lincoln degree
Mamun Sarker of Gazipur was among 3,523 graduates who received degrees from the University of Nebraska-Lincoln during commencement exercises May 13 and 14. Sarker earned a Doctor of Philosophy fro...
May, 16 2022 - Verified by University of Nebraska-Lincoln
Mamun Sarker was recognized for earning an academic award
Dean's Honor Award 2012
Added by Mamun
Postdoctoral Research Associate at University of Nebraksa-Lincoln
June 2022 - Present
Assistant Professor at the Dept. of Applied Chemistry and Chemical Engineering at Noalkhali Science and Technology University, Bangladesh
October 2017 - September 2023
Lecturer at the Dept. of Applied Chemistry and Chemical Engineering at Noalkhali Science and Technology University, Bangladesh
October 2015 - September 2017
Deposition temperature-mediated growth of helically shaped polymers and chevron-type graphene nanoribbons from a fluorinated precursor
Abstract: Graphene nanoribbons (GNRs) of precise size and shape, critical for controlling electronic properties and future device applications, can be realized via precision synthesis on surfaces using rationally designed molecular precursors. Fluorine-bearing precursors have the potential to form GNRs on nonmetallic substrates suitable for device fabrication. Here, we investigate the deposition temperature-mediated growth of a new fluorine-bearing precursor, 6,11-diiodo-1,4-bis(2-fluorophenyl)-2,3-diphenyltriphenylene (C42H24F2I2), into helically shaped polymer intermediates and chevron-type GNRs on Au(111) by combining scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory simulations. The fluorinated precursors do not adsorb on the Au(111) surface at lower temperatures, necessitating an optimum substrate temperature to achieve maximum polymer and GNR lengths. We compare the adsorption behavior with that of pristine chevron precursors and discuss the effects of C-H and C-F bonds. The results elucidate the growth mechanism of GNRs with fluorine-bearing precursors and establish a foundation for future synthesis of GNRs on nonmetallic substrates.
August 2024 -
Articles
Topological Solitons in Square-root Graphene Nanoribbons Controlled by Electric Fields
Abstract: Graphene nanoribbons (GNRs) are unique quasi-one-dimensional (1D) materials that have garnered a lot of research interest in the field of topological insulators. While the topological phases exhibited by GNRs are primarily governed by their chemical structures, the ability to externally control these phases is crucial for their potential utilization in quantum electronics and spintronics. Here we propose a class of GNRs featured by mirror symmetry and four zigzag segments in a unit cell that has unique topological properties induced and controlled by an externally applied electric field. Their band structures manifest two finite gaps which support topological solitons, as described by an effective square-root model. To demonstrate the experimental feasibility, we design and synthesize a representative partially zigzag chevron-type GNR (pzc-GNR) with the desired zigzag segments using a bottom-up approach. First-principles calculations on pzc-GNR reveal band inversions at the two finite gaps by switching the direction of the electric field, which is in accordance with predictions from the square-root Hamiltonian. We show different topological phases can be achieved by controlling the direction of the field and the chemical potential of the system in square-root GNRs. Consequently, upon adding a step-function electric field, solitons states can be generated at the domain wall. We discuss the properties of two types of soliton states, depending on whether the terminating commensurate unit cell is mirror symmetric.
June 2024 -
Articles
Porous Nanographenes, Graphene Nanoribbons, and Nanoporous Graphene Selectively Synthesized from the Same Molecular Precursor
Abstract: We demonstrate a family of molecular precursors based on 7,10-dibromo-triphenylenes that can selectively produce different varieties of atomically precise porous graphene nanomaterials through the use of different synthetic environments. Upon Yamamoto polymerization of these molecules in solution, the free rotations of the triphenylene units around the C–C bonds result in the formation of cyclotrimers in high yields. In contrast, in on-surface polymerization of the same molecules on Au(111) these rotations are impeded, and the coupling proceeds toward the formation of long polymer chains. These chains can then be converted to porous graphene nanoribbons (pGNRs) by annealing. Correspondingly, the solution-synthesized cyclotrimers can also be deposited onto Au(111) and converted into porous nanographenes (pNGs) via thermal treatment. Thus, both processes start with the same molecular precursor and end with a porous graphene nanomaterial on Au(111), but the type of product, pNG or pGNR, depends on the specific coupling approach. We also produced extended nanoporous graphenes (NPGs) through the lateral fusion of highly aligned pGNRs on Au(111) that were grown at high coverage. The pNGs can also be synthesized directly in solution by Scholl oxidative cyclodehydrogenation of cyclotrimers. We demonstrate the generality of this approach by synthesizing two varieties of 7,10-dibromo-triphenylenes that selectively produced six nanoporous products with different dimensionalities. The basic 7,10-dibromo-triphenylene monomer is amenable to structural modifications, potentially providing access to many new porous graphene nanomaterials. We show that by constructing different porous structures from the same building blocks, it is possible to tune the energy band gap in a wide range.
May 2024 -
Articles
Tunable Magnetic Coupling in Graphene Nanoribbon Quantum Dots
Abstract
Carbon-based quantum dots (QDs) enable flexible manipulation of electronic behavior at the nanoscale, but controlling their magnetic properties requires atomically precise structural control. While magnetism is observed in organic molecules and graphene nanoribbons (GNRs), GNR precursors enabling bottom-up fabrication of QDs with various spin ground states have not yet been reported. Here the development of a new GNR precursor that results in magnetic QD structures embedded in semiconducting GNRs is reported. Inserting one such molecule into the GNR backbone and graphitizing it results in a QD region hosting one unpaired electron. QDs composed of two precursor molecules exhibit nonmagnetic, antiferromagnetic, or antiferromagnetic ground states, depending on the structural details that determine the coupling behavior of the spins originating from each molecule. The synthesis of these QDs and the emergence of localized states are demonstrated through high-resolution atomic force microscopy (HR-AFM), scanning tunneling microscopy (STM) imaging, and spectroscopy, and the relationship between QD atomic structure and magnetic properties is uncovered. GNR QDs provide a useful platform for controlling the spin-degree of freedom in carbon-based nanostructures.
February 2024 -
Articles
Hybrid Edge Results in Narrowed Band Gap: Bottom-up Liquid-Phase Synthesis of Bent N = 6/8 Armchair Graphene Nanoribbons
Abstract: Scalable fabrication of graphene nanoribbons with narrow band gaps has been a nontrivial challenge. Here, we have developed a simple approach to access narrow band gaps using hybrid edge structures. Bottom-up liquid-phase synthesis of bent N = 6/8 armchair graphene nanoribbons (AGNRs) has been achieved in high efficiency through copolymerization between an o-terphenyl monomer and a naphthalene-based monomer, followed by Scholl oxidation. An unexpected 1,2-aryl migration has been discovered, which is responsible for introducing kinked structures into the GNR backbones. The N = 6/8 AGNRs have been fully characterized to support the proposed structure and show a narrow band gap and a relatively high electrical conductivity. In addition, their application in efficient gas sensing has also been demonstrated.
January 2024 -
Articles
Sub-5 nm Contacts and Induced p–n Junction Formation in Individual Atomically Precise Graphene NanoribbonsClick
Abstract: This paper demonstrates the fabrication of nanometer-scale metal contacts on individual graphene nanoribbons (GNRs) and the use of these contacts to control the electronic character of the GNRs. We demonstrate the use of a low-voltage direct-write STM-based process to pattern sub-5 nm metallic hafnium diboride (HfB2) contacts directly on top of single GNRs in an ultrahigh-vacuum scanning tunneling microscope (UHV-STM), with all the fabrication performed on a technologically relevant semiconductor silicon substrate. Scanning tunneling spectroscopy (STS) data not only verify the expected metallic and semiconducting character of the contacts and GNR, respectively, but also show induced band bending and p–n junction formation in the GNR due to the metal–GNR work function difference. Contact engineering with different work function metals obviates the need to create GNRs with different characteristics by complex chemical doping. This is a demonstration of the successful fabrication of precise metal contacts and local p–n junction formation on single GNRs
August 2023 -
Articles
Diffusion-controlled on-surface synthesis of graphene nanoribbon heterojunctions
Abstract: We report a new diffusion-controlled on-surface synthesis approach for graphene nanoribbons (GNR)
consisting of two types of precursor molecules, which exploits distinct differences in the surface
mobilities of the precursors. This approach is a step towards a more controlled fabrication of complex
GNR heterostructures and should be applicable to the on-surface synthesis of a variety of GNR
heterojunctions.
February 2022 -
Articles
