Molecular Nanoscale Research Articles

A Comparative Analysis of SARS-CoV-2 Variants of Concern (VOC) Spike Proteins Interacting with hACE2 Enzyme.

In late 2019, the emergence of a novel coronavirus led to its identification as SARS-CoV-2, precipitating the onset of the COVID-19 pandemic. Many experimental and computational studies were performed on SARS-CoV-2 to understand its behavior and patterns. In this research, Molecular Dynamic (MD) simulation is utilized to compare the behaviors of SARS-CoV-2 and its Variants of Concern (VOC)-Alpha, Beta, Gamma, Delta, and Omicron-with the hACE2 protein. Protein structures from the Protein Data Bank (PDB) were aligned and trimmed for consistency using Chimera, focusing on the receptor-binding domain (RBD) responsible for ACE2 interaction. MD simulations were performed using Visual Molecular Dynamics (VMD) and Nanoscale Molecular Dynamics (NAMD2), and salt bridges and hydrogen bond data were extracted from the results of these simulations. The data extracted from the last 5 ns of the 10 ns simulations were visualized, providing insights into the comparative stability of each variant's interaction with ACE2. Moreover, electrostatics and hydrophobic protein surfaces were calculated, visualized, and analyzed. Our comprehensive computational results are helpful for drug discovery and future vaccine designs as they provide information regarding the vital amino acids in protein-protein interactions (PPIs). Our analysis reveals that the Original and Omicron variants are the two most structurally similar proteins. The Gamma variant forms the strongest interaction with hACE2 through hydrogen bonds, while Alpha and Delta form the most stable salt bridges; the Omicron is dominated by positive potential in the binding site, which makes it easy to attract the hACE2 receptor; meanwhile, the Original, Beta, Delta, and Omicron variants show varying levels of interaction stability through both hydrogen bonds and salt bridges, indicating that targeted therapeutic agents can disrupt these critical interactions to prevent SARS-CoV-2 infection.

Peculiar wetting behavior of nanodroplets comprising antagonistic alcohol-water mixtures on a graphene surface

Binary mixtures, consisting of partially and totally wetting liquids with respect to a specific substrate and known as an antagonistic mixture, are commonly encountered. Although the wetting behavior of antagonistic mixtures deviates from that of conventional liquids, studies exploring this phenomenon are scarce. At the nanoscale, the wetting behavior of nanodroplets containing such mixtures may diverge even further from our established understanding. Employing Nanoscale Molecular Dynamics simulations, we explore the wetting behavior of nanodroplets containing mixtures of water (partial wetting) and ethanol or isopropanol (total wetting) on a graphene surface. By adjusting the water fraction (xw) in the antagonistic mixture, three distinct wetting states have been identified: (I) In total wetting regime (low xw), spontaneous spreading is observed; (II) In plateau regime (medium xw), alcohol leakage from the droplet occurs, with the apparent contact angle (CA) remaining constant; (III) In partial wetting regime (high xw), the CA increases with xw and alcohol molecules tend to accumulate at the contact line. Unexpectedly, the spreading coefficient (S) remains positive and turns negative only as xw near unity. Furthermore, Young's equation proves to be inapplicable even when S < 0. These peculiar wetting phenomena are comprehensively discussed and elucidated.

The Dynamics of Per- and Polyfluoroalkyl Substances (PFAS) at Interfaces in Porous Media: A Computational Roadmap from Nanoscale Molecular Dynamics Simulation to Macroscale Modeling.

Managing and remediating perfluoroalkyl and polyfluoroalkyl substance (PFAS) contaminated sites remains challenging. The major reasons are the complexity of geological media, partly unknown dynamics of the PFAS in different phases and at fluid-fluid and fluid-solid interfaces, and the presence of cocontaminants such as nonaqueous phase liquids (NAPLs). Critical knowledge gaps exist in understanding the behavior and fate of PFAS in vadose and saturated zones and in other porous media such as concrete and asphalt. The complexity of PFAS-surface interactions warrants the use of advanced characterization and computational tools to understand and quantify nanoscale behavior of the molecules. This can then be upscaled to the microscale to develop a constitutive relationship, in particular to distinguish between surface and bulk diffusion. The dominance of surface diffusion compared to bulk diffusion results in the solutocapillary Marangoni effect, which has not been considered while investigating the fate of PFAS. Without a deep understanding of these phenomena, derivation of constitutive relationships is challenging. The current Darcy scale mass-transfer models use constitutive relationships derived from either experiments or field measurements, which makes their applicability potentially limited. Here we review current efforts and propose a roadmap for developing Darcy scale transport equations for PFAS. We find that this needs to be based on systematic upscaling of both experimental and computational studies from nano- to microscales. We highlight recent efforts to undertake molecular dynamics simulations on problems with similar levels of complexity and explore the feasibility of conducting nanoscale simulations on PFAS dynamics at the interface of fluid pairs.

Novel benzothiazole sulfonamides as potent α-glucosidase and cholinesterase inhibitors: Design, synthesis, structural properties, biological evaluation and docking studies

A simplified synthetic method yielded diverse 2-aminobenzothiazole variants through sulfonylation and amino group alkylation. Extensive characterization via X-ray diffraction, UV/vis, infrared, 1H, and 13CNMR spectroscopies was performed. Compounds 19, 25, 29, 33, and 37 displayed dose-dependent α-glucosidase inhibition, with IC50 values, compared to acarbose, of 79.35 ± 1.13 µM, 139.53 ± 1.12 µM, 172.16 ± 1.23 µM, 179.35 ± 1.13 µM, and 97.36 ± 1.15 µM, respectively. For BChE (Butyrylcholinesterase) inhibition, compounds 25, 31, 32, 36, 37, 38, and 39 exhibited IC50 values, compared to Eserine, of 153.73 ± 1.17 µM, 175.64 ± 1.13 µM, 252.98 ± 1.19 µM, 124.92 ± 1.17 µM, 286.38 ± 1.16 µM, 128.62 ± 1.18 µM, and 97.28 ± 1.15 µM. Molecular docking validated these results, linking structure to activity and assessing α-glucosidase inhibition. Detailed ligand-protein interactions were explored, illuminating bond types and atomic distances within the active site, particularly for acarbose. Compound 29, indicated by its small Eg value, exhibited high reactivity due to specific electron density and structural features. Drug-likeness was evaluated using multiple criteria and compared favorably to existing drugs like penfluridol and amiodarone. NAMD (Nanoscale Molecular Dynamics) simulated ligand-protein complex behavior in a cell-like context and used Root Mean Square Deviation (RMSD) to assess stability and conformational changes. Computationally determined SASA values evaluated water molecule accessibility and stability. Compound stability and solvent interactions in ligand-protein complexes highlighted compound 33 as most stable, while compounds 19 and 37 resembled acarbose, and compound 25 achieved stability over time. These findings enhance comprehension of solid-state arrangements of novel aminobenzothiazole sulfonamide derivatives, potentially stimulating further research for drug discovery within the scientific community.

Uridylation of the histone mRNA stem-loop weakens binding interactions with SLBP while maintaining interactions with 3’hExo

ABSTRACT Histone mRNA degradation is controlled by the unique 3’ stem-loop of histone mRNA and the stem-loop binding protein (SLBP). As part of this process, the 3’ stem-loop is trimmed by the histone-specific 3’ exonuclease (3’hExo) and uridylated by the terminal uridylyl transferase 7 (TUT7), creating partially degraded intermediates with short uridylations. The role of these uridylations in degradation is not fully understood. Our work examines changes in the stability of the ternary complex created by trimming and uridylation of the stem-loop to better understand the role of this process in the histone mRNA life cycle. In this study, we used fluorescence polarization and electrophoretic mobility shift assays to demonstrate that both SLBP and 3’hExo can bind to uridylated and partially degraded stem-loop intermediates, although with lower affinity. We further characterized this complex by performing 1-µs molecular dynamics simulations using the AMBER force field and Nanoscale Molecular Dynamics (NAMD). These simulations show that while uridylation helps maintain the overall shape of the stem-loop, the combination of uridylation and dephosphorylation of the TPNK motif in SLBP disrupts key RNA–protein interactions. They also demonstrate that uridylation allows 3’hExo to maintain contact with the stem-loop after partial degradation and plays a role in disrupting key base pairs in partially degraded histone mRNA intermediates. Together, these experiments and simulations suggest that trimming by 3’hExo, uridylation, and SLBP dephosphorylation weakens both RNA–protein interactions and the stem-loop itself. Our results further elucidate the role of uridylation and SLBP dephosphorylation in the early stages of histone mRNA degradation.

The curious case of the disassembling ATP synthase studied using molecular dynamics simulations.

Cellular bioenergetic processes responsible for providing energy to most lifeforms, photosynthesis and respiration, involve cooperative networks of proteins integrated into membrane domains. Exascale computational approaches, hand-in-hand with experiments, are necessary to learn how these processes are achieved. In particular, computations will reveal key organizational principles that underlie the efficient energy harvesting of protein networks. Application of these principles will aid the design of better man-made biohybrid devices in order to harness renewable energy for the world's future energy needs. The universal process of ATP synthesis, a component of the photosynthetic energy harvesting and respiration can now be investigated at atomic detail through the molecular dynamics of a complex biological motor, ATP synthase, that transforms an ion gradient existing across the cell membrane into the synthesis of ATP from ADP. The reversibility of this biomotor is essential for energy-transcending processes in all living systems, yet, the mechanism of its action remains fragmentary. To investigate this mechanism, we performed simulations on full bacterial and bovine F-type ATPase models utilizing Nanoscale Molecular Dynamics software. First, we monitored a water channel located near key acidic residues in the bacterial ATPase c-ring to observe its behavior both before and after proton transfer occurred in this region, and we discovered what we hypothesize to be a mechanism that prevents the back-transport of protons. Second, we designed models for the bovine ATPase to examine its overall stability, degree of water leakage in the membrane-inserted region, and “hook” (subunit e) behavior in the presence of varying voltages. We have preliminarily highlighted the instability of the catalytic stock and significant unfolding of the hook in all models, as well as increased water leakage in models that did not contain a lipid plug inserted into the c-ring.

Switching in Nanoscale Molecular Junctions due to Contact Reconfiguration

Switching effects are key elements in the design and characterization of nanoscale molecular electronics systems. They are used to achieve functionality through the transition between different conducting states. In this study, we analyze the presence of switching events in reference molecular systems, which are not designed to have switching behavior, such as oligo(phenylene ethynylene)s and alkanes, using the mechanically controllable break junction technique. These events can be classified in two groups, depending on whether the breaking trace shows exponential decay or plateau-like features before the switch happens. We argue that the former correspond to junctions forming after rupture of the gold atomic point contact, while the latter can be related to a change in the contact geometry of the junction. These results highlight how a proper choice of anchoring group and careful comparison with reference compounds are essential to understanding the origin of switching in molecular break junctions.

Species Differences in Response to Binding Interactions of Bisphenol A and its Analogs with the Modeled Estrogen Receptor 1 and In Vitro Reporter Gene Assay in Human and Zebrafish.

Adverse impacts associated with the interactions of numerous endocrine-disruptor chemicals (EDCs) with estrogen receptor 1 play a pivotal role in reproductive dysfunction. The predictive studies on these interactions thus are crucial in the risk assessment of EDCs but rely heavily on the accuracy of specific protein structure in three dimensions. As the three-dimensional (3D) structure of zebrafish estrogen receptor 1 (zEsr1) is not available, the 3D structure of zEsr1 ligand-binding domain (zEsr1-LBD) was generated using MODELLER and its quality was assessed by the PROCHECK, ERRAT, ProSA, and Verify-3D tools. After the generated model was verified as reliable, bisphenol A and its analogs were docked on the zEsr1-LBD and human estrogen receptor 1 ligand-binding domain (hESR1-LBD) using the Discovery Studio and Autodock Vina programs. The molecular dynamics followed by molecular docking were simulated using the Nanoscale Molecular Dynamics program and compared to those of the in vitro reporter gene assays. Some chemicals were bound with an orientation similar to that of 17β-estradiol in both models and in silico binding energies showed moderate or high correlations with in vitro results (0.33 ≤ r2 ≤ 0.71). Notably, hydrogen bond occupancy during molecular dynamics simulations exhibited a high correlation with in vitro results (r2 ≥ 0.81) in both complexes. These results show that the combined in silico and in vitro approaches is a valuable tool for identifying EDCs in different species, facilitating the assessment of EDC-induced reproductive toxicity. Environ Toxicol Chem 2022;41:2431-2443. © 2022 SETAC.

Computational and Biophysical Analysis of RNA/Protein Complexes in Histone mRNA Degradation

Histone mRNA is the only known metazoan mRNA that is not polyadenylated at its 3’ end; instead, it ends in a highly conserved stem‐loop. This stem‐loop and its protein binding partner, the stem‐loop binding protein (SLBP), control every aspect of histone mRNA metabolism. As the cell prepares to degrade histone mRNA in the cytoplasm towards the end of S‐phase, both of these elements are modified; the mRNA is trimmed by 3’ human exonuclease (3’hExo) and uridylated by a terminal uridylyl transferase, while SLBP is dephosphorylated. The trimming and uridylation process creates uridylated intermediates that differ in length as the histone mRNA begins to undergo degradation, while the dephosphorylation of SLBP destabilizes the protein. Both of these events are associated with histone mRNA degradation, their exact roles in histone mRNA metabolism are not fully understood. In this study, we seek to characterize how these changes to SLBP and histone mRNA affect the stability of the ternary SLBP/3’hEXO/mRNA complex using both computational and experimental methods. To computationally characterize the effects of uridylation on stability of the ternary complex, we performed molecular dynamics simulations (1 µs) using AMBER force fields and Nanoscale Molecular Dynamics (NAMD). To experimentally characterize these observations, we used a fluorescence‐based EMSA competition assay to measure the proteins’ difference in affinity for the wild‐type stem‐loop and uridylated intermediates. Through these experiments, we have gained valuable insight into the role of both the uridylation of histone mRNA and the dephosphorylation of SLBP at the beginning of histone mRNA degradation.

Principal Component Analysis of Surface-Enhanced Raman Scattering Spectra Revealing Isomer-Dependent Electron Transport in Spiropyran Molecular Junctions: Implications for Nanoscale Molecular Electronics.

The characterization of single-molecule structures could provide significant insights into the operation mechanisms of functional devices. Structural transformation via isomerization has been extensively employed to implement device functionalities. Although single-molecule identification has recently been achieved using near-field spectroscopy, discrimination between isomeric forms remains challenging. Further, the structure–function relationship at the single-molecule scale remains unclear. Herein, we report the observation of the isomerization of spiropyran in a single-molecule junction (SMJ) using simultaneous surface-enhanced Raman scattering (SERS) and conductance measurements. SERS spectra were used to discriminate between isomers based on characteristic peaks. Moreover, conductance measurements, in conjunction with the principal component analysis of the SERS spectra, clearly showed the isomeric effect on the conductance of the SMJ.

Polymer Topology Reinforced Synergistic Interactions among Nanoscale Molecular Clusters for Impact Resistance with Facile Processability and Recoverability

AbstractThe intrinsic conflicts between mechanical performances and processability are main challenges to develop cost‐effective impact‐resistant materials from polymers and their composites. Herein, polyhedral oligomeric silsesquioxanes (POSSs) are integrated as side chains to the polymer backbones. The one‐dimension (1D) rigid topology imposes strong space confinements to realize synergistic interactions among POSS units, reinforcing the correlations among polymer chains. The afforded composites demonstrate unprecedented mechanical properties with ultra‐stretchability, high rate‐dependent strength, superior impact‐resistant capacity as well as feasible processability/recoverability. The hierarchical structures of the hybrid polymers enable the co‐existence of multiple dynamic relaxations that are responsible for fast energy dissipation and high mechanical strengths. The effective synergistic correlation strategy paves a new pathway for the design of advanced cluster‐based materials.

Polymer Topology Reinforced Synergistic Interactions among Nanoscale Molecular Clusters for Impact Resistance with Facile Processability and Recoverability

AbstractThe intrinsic conflicts between mechanical performances and processability are main challenges to develop cost‐effective impact‐resistant materials from polymers and their composites. Herein, polyhedral oligomeric silsesquioxanes (POSSs) are integrated as side chains to the polymer backbones. The one‐dimension (1D) rigid topology imposes strong space confinements to realize synergistic interactions among POSS units, reinforcing the correlations among polymer chains. The afforded composites demonstrate unprecedented mechanical properties with ultra‐stretchability, high rate‐dependent strength, superior impact‐resistant capacity as well as feasible processability/recoverability. The hierarchical structures of the hybrid polymers enable the co‐existence of multiple dynamic relaxations that are responsible for fast energy dissipation and high mechanical strengths. The effective synergistic correlation strategy paves a new pathway for the design of advanced cluster‐based materials.

A Bubble‐Assisted Approach for Patterning Nanoscale Molecular Aggregates

AbstractWe demonstrate a new approach to pattern functional organic molecules with a template of foams, and achieve a resolution of sub 100 nm. The bubble‐assisted assembly (BAA) process is consisted of two periods, including bubble evolution and molecular assembly, which are dominated by the Laplace pressure and molecular interactions, respectively. Using TPPS (meso‐tetra(4‐sulfonatophenyl) porphyrin), we systematically investigate the patterns and assembly behaviour in the bubble system with a series of characterizations, which show good uniformity in nanoscale resolution. Theoretical simulations reveal that TPPS's J‐aggregates contribute to the ordered construction of molecular patterns. Finally, we propose an empirical rule for molecular patterning approach, that the surfactant and functional molecules should have the same type of charge in a two‐component system. This approach exhibits promising feasibility to assemble molecular patterns at nanoscale resolution for micro/nano functional devices.

A Bubble-Assisted Approach for Patterning Nanoscale Molecular Aggregates.

We demonstrate a new approach to pattern functional organic molecules with a template of foams, and achieve a resolution of sub 100 nm. The bubble-assisted assembly (BAA) process is consisted of two periods, including bubble evolution and molecular assembly, which are dominated by the Laplace pressure and molecular interactions, respectively. Using TPPS (meso-tetra(4-sulfonatophenyl) porphyrin), we systematically investigate the patterns and assembly behaviour in the bubble system with a series of characterizations, which show good uniformity in nanoscale resolution. Theoretical simulations reveal that TPPS's J-aggregates contribute to the ordered construction of molecular patterns. Finally, we propose an empirical rule for molecular patterning approach, that the surfactant and functional molecules should have the same type of charge in a two-component system. This approach exhibits promising feasibility to assemble molecular patterns at nanoscale resolution for micro/nano functional devices.

Modeling Group II Chaperonin “Heat Shock” Protein Structure: pH and temperature dependency Piyasi Ghosh1,2 Vivek Govind Kumar1,3 Mahmoud Moradi3 Ruben Michael Ceballos1,2,4 University of Arkansas, Cell and Molecular Biology Program University of Arkansas, Department of Biological Sciences University of Arkansas, Department of Chemistry and Biochemistry Arkansas Center for Space and Planetary Sciences Program

Group II chaperonins or “heat shock proteins” (HSPs) are expressed in hyperthermophilic archaea of the family Sulfolobaceae. Three chaperonins designated as HSPα, HSPβ, and HSPγ have been reported and serve as subunits in the formation of nonameric double-ring (18-mer) complexes. HSP complexes in nature function to protect cellular proteins (e.g., enzymes) during thermal shock and, perhaps, other stressors such as pH flux. HSPα and HSPβ are stoichiometrically favored in HSP complex formation, whereas the HSPγ subunit is more rarely found as a constituent subunit. In vitro, HSPα homomers, HSPβ homomers, and HSPα/HSPβ heteromers will form in the presence of ATP and divalent cations (e.g., Mg++). HSP complexes feature a central pore that leads to an internal cavity. Pore openings are found at both apical and basal extremities of the 18-mer complex. It has been suggested that HSPs have “opened” and “closed” states. Whether the pore is “opened” or “closed” is a function of conformational changes in the individual HSP subunits that lead to subunit rearrangements in the complex. Since the thermotolerant nature and protective function of HSP complexes is likely based on the ability of the system to open and close, it is of interest to understand the changes in subunit ultra-structure that mediate switching between to these two conformational states. In this study, molecular dynamics simulations were conducted test the relative stability of HSPα versus HSPβ and to determine how HSPα and HSPβ tertiary structure may be impacted by temperature and pH. SWISS-MODEL and PyMOL were used to generate the 3-D HSP structures. CHARMM-GUI solution builder was used to solvate the modeled structures in a “water box” as an energy minimization step prior to running simulations, which were performed in Nanoscale Molecular Dynamics (NAMD). Output was later visualized using Visual Molecular Dynamics (VMD). We demonstrate that HSP a-helical structures change conformation as pH drops from neutral to acidic. Our data suggest that changes in subunit structure under thermal shock lead to changes in pore diameter; however, it is unclear if pH flux influences opening and closing of the HSP complex pore. These results demonstrate a plausible biophysical mechanism by which group II chaperonin complexes change conformation while serving client proteins.

Nanoscale Molecular Quantification of Stem Cell-Hydrogel Interactions.

A common approach to tailoring synthetic hydrogels for regenerative medicine applications involves incorporating RGD cell adhesion peptides, yet assessing the cellular response to engineered microenvironments at the nanoscale remains challenging. To date, no study has demonstrated how RGD concentration in hydrogels affects the presentation of individual cell surface receptors. Here we studied the interaction between human mesenchymal stem cells (hMSCs) and RGD-functionalized poly(ethylene glycol) hydrogels, by correlating macro- and nanoscale single-cell interfacial quantification techniques. We quantified RGD unbinding forces on a synthetic hydrogel using single cell atomic force spectroscopy, revealing that short-term binding of hMSCs was sensitive to RGD concentration. We also performed direct stochastic optical reconstruction microscopy (dSTORM) to quantify the molecular interactions between integrin α5β1 and a biomaterial, unexpectedly revealing that increased integrin clustering at the hydrogel-cell interface correlated with fewer available RGD binding sites. Our complementary, quantitative approach uncovered mechanistic insights into specific stem cell-hydrogel interactions, where dSTORM provides nanoscale sensitivity to RGD-dependent differences in cell surface localization of integrin α5β1. Our findings reveal that it is possible to precisely determine how peptide-functionalized hydrogels interact with cells at the molecular scale, thus providing a basis to fine-tune the spatial presentation of bioactive ligands.

A Molecular Dynamics Simulation of the Toluene-Water Interface in the Presence of an External Magnetic Field

Among the current techniques in the stabilizing the emulsion, the magnetic treatment is attracting more attention during past years. In this work, a molecular dynamics simulation was performed to investigate the effect of an external magnetic field on the toluene-water interface. An extended version of Nanoscale Molecular Dynamics (NAMD) source code including the magnetic field feature was used to do all MD calculations. The radial distribution function (RDF), the integration RDF, and the non-bonded energy of three pairs atoms, beside the interfacial tension (IFT) values in the presence of different magnetic field intensities have been calculated and reported in this paper. The changes in the potential of the interaction has been proved by analyzing the RDF and integration RDF plots. The obtained results showed that the increase of IFT is only appeared within a specific range of magnetic field intensities. Moreover, the IFT decreases when the magnetic field intensity is increased. The simulation results provide an elementary understanding of the applying magnetic treatment as a technique in the preparing of emulsion system.

Nanoscale Molecular Characterization of Hair Cuticle Cells Using Integrated Atomic Force Microscopy-Infrared Laser Spectroscopy.

The hair cuticle provides significant protection from external sources, as well as giving rise to many of its bulk properties, e.g., friction, shine, etc. that are important in many industries. In this work, atomic force microscopy-infrared spectroscopy (AFM-IR) has been used to investigate the nanometer-scale topography and chemical structure of human hair cuticles in two spectral regions. AFM-IR combines atomic force microscopy with a tunable infrared laser and circumvents the diffraction limit that has impaired traditional infrared spectroscopy, facilitating surface-selective spectroscopy at ultra-spatial resolution. This high resolution was exploited to probe the protein secondary structures and lipid content, as well as specific amino acid residues, e.g., cystine, within individual cuticle cells. Characterization across the top of individual cells showed large inhomogeneity in protein and lipid contributions that suggested significant changes to physical properties on approaching the hair edge. Additionally, the exposed layered sub-structure of individual cuticle cells allowed their chemical compositions to be assessed. The variation of protein, lipid, and cystine composition in the observed layers, as well as the measured dimensions of each, correspond closely to that of the epicuticle, A-layer, exocuticle, and endocuticle layers of the cuticle cell sub-structure, confirming previous findings, and demonstrate the potential of AFM-IR for nanoscale chemical characterization within biological substrates.

Nanoscale Molecular Composition of Solid Bitumen from the Eagle Ford Group across a Natural Thermal Maturity Gradient

Microscopic solid bitumen is a petrographically defined secondary organic matter residue produced during petroleum generation and subsequent oil transformation. The presence of solid bitumen impact...

Nanoscale Molecular Building Blocks for Layer‐by‐Layer Assembly

AbstractUltrathin molecular films can be used as building blocks to enable rational design of functionalities at the molecular level. A versatile and scalable approach to fabricate transfer‐compatible ultrathin molecular films with a broad range of physiochemical properties is reported. Different molecules in layers of uniform nanoscale thickness are deposited on monolayer hexagonal boron nitride (ML h‐BN) film. Initially, the deposited molecules form islands due to limited molecular diffusion during deposition on ML h‐BN, but postannealing effectively transforms them to the thermodynamically preferred film structures. Ultrathin building blocks composed of ML h‐BN and different molecules (C60, pentacene, C44H32N2) are realized, then transferred layer‐by‐layer (L‐by‐L) to form materials with precisely controlled composition and thickness, including donor/acceptor superlattices. This approach can facilitate the integration of nanoscale molecules with different material platforms for advanced functionalities.