ChemRxiv
Not a member yet
27047 research outputs found
Sort by
A review of recent theoretical advances in polymer brushes
No full textIn this article, I review my recent theoretical approaches to polymer brushes. By
means of the density functional theory (DFT) and the molecular dynamic simulations
(MD), the detailed behaviors of polymer brushes are revealed in different situations.
It turns out that polymer brush bilayers show shear thinning effect under stationary
shear motion only when there is hydrodynamic interactions between monomers. Also,
by studying charged brush bilayers under non-equilibrium shear inversion, I reveal that
the hydrodynamic interactions are responsible for the mechanical instabilities in the
brush bilayers and also I show that the electrostatic interactions between monomers
completely suppress these mechanical instabilities. The findings of this study sheds
light on our understanding of polymer brushes as a complicated example of soft matter
and biological system
Parameterization of a Fluctuating Charge Model for Complexes Containing 3d Transition Metals
No full textMetalloproteins widely exist in biology, playing pivotal roles in diverse life processes. Meanwhile, molecular dynamics (MD) simulations, which are driven by classical force fields, have emerged as indispensable tools in scientific research. Among the critical parameters within classical force fields are partial charges, which are traditionally derived from quantum mechanical (QM) calculations. However, QM calculations are often time-insensitive and prone to basis set dependence. Alternatively, fluctuating charge (FQ) models offer a promising avenue for partial charge derivation, boasting significant speed advantages conducive to large-scale screening. Building upon our previous work, which tailored an FQ model for zinc-containing complexes, we have extended this model to include additional 3d transition metals integral to the life sciences, namely chromium, manganese, iron, cobalt, and nickel. Employing CM5 charges as reference points for parameterization, our FQ model accurately reproduces partial charges for 3d metal complexes featuring biologically relevant ligands. Furthermore, by using atomic charges derived by our FQ model, MD simulations have been performed, and the results show excellent performance in simulating proteomic metal sites housing multiple metal ions. Specifically, our simulations accurately capture the behavior of a metalloprotein containing an iron-sulfur cluster and another containing a di-manganese metal site. These results showcase comparable performance to those of RESP charges. We anticipate that our study can accelerate the parameterization of atomic charges, thereby facilitating simulations of metalloproteins featuring 3d transition metals
Molybdenum Disulfide MoS2 and the q-BWF line shapes (Raman Spectroscopy)
No full textRRUFF database is proposing the Raman spectra of two molybdenum disulfide MoS_2 samples. Here we show the q-BWF fitted functions to the E_2g and A_1g Raman bands of these samples. The q-BWF functions are generalizing the Breit-Wigner-Fano line shape in the framework of the q-exponential function proposed by Constantino Tsallis and his statistics. The fitted q-BWF functions to pyramid and monolayer Raman spectra by Fabbri et al., 2022, are also proposed. Some review of Raman spectroscopy of MoS_2 is proposed too, especially about Fano-Raman and Davydov splitting effect
Automated experiment and data generation by foundation models for synthesizing polyamic acid particles
No full textThis study proposes an automated system for synthesizing polyamic acid particles using a custom liquid-handling device and a robotic arm. Integrating cameras and a multimodal large language model facilitates continuous monitoring and documentation, enhancing objectivity in synthetic experiments, and enabling future advancements in experimental research
Inverse Photoemission Spectroscopy of Coinage Metal Corroles: Comparison with Solution-Phase Electrochemistry
No full textA combined direct and inverse photoemission study of coinage metal corroles suggests that the latter technique, in favorable cases, can provide some additional information relative to electrochemical measurements. Thus, whereas inverse photoemission spectroscopy (IPES) provides relative electron affinities for electron addition to different unoccupied orbitals, electrochemical reduction potentials sheds light on the energetics of successive electron additions. While all three coinage metal triphenylcorrole (TPC) complexes exhibit similar ionization potentials, they exhibit dramatically different inverse photoemission spectra. For Cu[TPC], the lowest-energy IPES feature (0.74 eV) is found to be exceedingly close to the Fermi level; it is significantly higher for Ag[TPC] (1.65 eV) and much higher for Au[TPC] (2.40 eV). These differences qualitatively mirror those observed for electrochemical reduction potentials and are related to a partially metal-centered LUMO in the case of Cu- and Ag[TPC] and a fully corrole-based LUMO in the case of Au[TPC]; the latter orbital corresponds to the LUMO+1 in the case of Ag[TPC]
Site-Selective Photobromination of O-Acetylated Carbohydrates in Benzotrifluoride
No full textThe Ferrier photobromination enables direct synthetic access to valuable 5-C-bromosugars but has limitations which restrict its broader use. The reaction is typically conducted in CCl4 heated at reflux with irradiation by broad spectrum, energy inefficient heat lamps. Herein, we demonstrate that the reaction proceeds rapidly and efficiently with PhCF3 as a safe and environmentally benign alternative to CCl4 at mild temperatures (≤ 40 °C) inside a compact photoreactor fitted with purple LEDs
Direct excitation of carbonyl cyclopropanes: From divergent photo-isomerization and annulation to unified reductive C-C cleavage
No full textWe report herein our studies on the direct photoactivation of carbonyl cyclopropanes to give biradical intermediates, leading to selective cleavage of the more substituted carbon-carbon bond. Depending on the substrate structure, extended alkenes were isolated or directly reacted in a photo-Nazarov process to give bicyclic products. Based on these results, a unified reductive ring-opening reaction was developed by using diphenyl disulfide as a HAT reagent. By performing a sequential cyclopropanation/selective ring opening reaction, we achieved a CH2 insertion into the alpha,beta- bond of both acyclic and cyclic unsaturated carbonyl compounds. Our protocol therefore provides a further tool for framework-editing of carbocycles, complementing the recent progress in "skeletal editing" strategies
Room-Temperature Strong Coupling between CdSe Nanoplatelets and a Metal–DBR Fabry–Pérot Cavity
No full textThe generation of exciton–polaritons through strong light–matter interactions represents an emerging platform for exploring quantum phenomena. A significant challenge in colloidal nanocrystal-based polaritonic systems is the ability to operate at room temperature with high fidelity. Here, we demonstrate the generation of room-temperature
exciton–polaritons through the coupling of CdSe nanoplatelets (NPLs) with a Fabry–Pérot optical cavity, leading to
a Rabi splitting of 74.6 meV. Quantum-classical calculations accurately predict the complex dynamics between the
many dark state excitons and the optically allowed polariton states, including the experimentally observed lower polariton photoluminescence emission, and the concentration of lower polariton photoluminescence intensities at higher
in-plane momenta as the cavity becomes more negatively detuned. The Rabi splitting measured at 5 K is similar to
that at 300 K, validating the feasibility of the temperature-independent operation of this polaritonic system. Overall,
these results show that CdSe NPLs are an excellent material to facilitate the development of room-temperature quantum
technologies
Solution characterization of zirconium oxo clusters
No full textGroup 4 metal oxo clusters are atomically precise models for colloidal nanocrystals as they consist of an inorganic core and an organic ligand shell. They are also important building blocks for MOFs, 3D-printing and polymers composites. Recently, we have elucidated their structure and ligand shell using solid state methods. Here we go one step further studying these materials in solution. Dynamic light scattering is a common technique to determine the solvodynamic diameter of nanocrystals. However, due to their small size, clusters present difficulties to the automatic data treatment, available in commercial software. Here we developed a data treatment method to fit DLS data of clusters, where we separate the signal into a contribution from the clusters itself combined with a contribution of number fluctuations. Additionally, diffusion ordered spectroscopy (DOSY) is used to study how these materials affect the viscosity of the solvent
Ultrathin Boron Growth onto Nanodiamond Surfaces via Electrophilic Boron Precursors
No full textDiamond as a templating substrate is largely unexplored and the unique properties of diamond including its large bandgap, thermal conductance and lack of cytotoxicity make it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high-temperature (HPHT) nanodiamonds NDs are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work we demonstrate a templated synthesis of ultrathin boron on ND surfaces using trigonal boron compounds. Boron trichloride (BCl3), boron tribromide (BBr3) and borane (BH3) were found to react with ND substrates at room temperature in inert conditions. BBr3 and BCl3 were highly reactive with the diamond surface and sheet-like structures were produced and was verified with electron microscopy. Surface sensitive spectros-copies were used to probe the molecular and atomic structure of the ND constructs’ surface and quantification showed the boron shell was less than 1 nm thick after 1-24 hour reaction protocols. Observations of the reaction supports a self-terminating mechanism, similar to atomic layer depo-sition growth and is likely due to the quenching of alcohols on the diamond surface. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mech-anism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing and BNCT