ChemRxiv
Not a member yet
27047 research outputs found
Sort by
Molecular asymmetry and rigidification as strategies to activate and enhance thermally activated delayed fluorescence in deep-blue MR-TADF emitters
No full textTwo novel deep-blue multi-resonant thermally activate delayed fluorescnece (MR-TADF) emitters, 1B-CzCrs and 2B-CzCrs, containing a a fused carbazole unit were synthesized. The carbazole contributed to the emergence of TADF in these small molecules. Particularly, organic light-emitting diodes with 1B-CzCrs doped in mCP host achieve a maximum external quantum efficiency of 12.8% at CIE coordinates of (0.146, 0.062)
HF trimer: A new full-dimensional potential energy surface and rigorous 12D quantum calculations of vibrational states
No full textHF trimer, as the lightest cyclic hydrogen-bonded (HB) trimer, has long been a favorite prototype system for spectroscopic and theoretical investigations of the structure, energetics, and dynamics of hydrogen-bond networks, and the role that nonadditive, three-body interactions play in shaping these properties. Recently, rigorous quantum 12D calculations of the coupled intra- and intermolecular vibrations of this fundamental HB trimer [P.M. Felker and Z. Bačić, J. Chem. Phys. 2023, 158, 234109] were performed, employing an older ab initio-based many-body potential energy surface (PES). While the theoretical results were found to be in reasonably good agreement with the available spectroscopic data, it was also evident that it is highly desirable to develop a more accurate 12D PES of HF trimer. Motivated by this, here we report a new 12D PES of this paradigmatic system. Approximately 42,540 geometries were sampled and calculated at the level of CCSD(T)-F12a/AVTZ. The permutationally invariant polynomial-neural network based Δ-machine learning approach [Y. Liu and J. Li, J. Phys. Chem. Lett. 2022, 13, 4729] was employed to perform cost-efficient calculations
of the basis-set-superposition error (BSSE) correction. By strategically selecting data points, this approach facilitated the construction of a high-precision PES with BSSE correction, while requiring only a minimal number of BSSE value computations. The fitting error of the final PES is only 0.035 kcal/mol. To assess its performance, the 12D fully coupled quantum calculations of excited intra- and intermolecular vibrational states of HF trimer are carried out using the rigorous methodology developed by us earlier. The results are found to be in a significantly better agreement with the available spectroscopic data than those obtained with the previously existing 12D PES
FRETting about CRISPR-Cas assays: Dual-channel reporting lowers detection limits and times-to-result
No full textCRISPR-Cas systems have evolved several mechanisms to specifically target foreign DNA. These properties have made them attractive as biosensors. The primary drawback associated with contemporary CRISPR-Cas biosensors is their weak signaling capacity, which is typically compensated for by coupling the CRISPR-Cas systems to nucleic acid amplification. This adds time and complexity to the diagnostic process, limiting the practicality of these assays for many clinical applications. An alternative strategy to improve signaling capacity is to engineer the reporter, i.e., design new signal-generating substrates for Cas proteins. Unfortunately, due to their reliance on custom synthesis or specialized analytical equipment, most of these engineered reporter substrates are inaccessible to many researchers. Herein, we present a substrate for Cas12a that functions as a seamless “drop-in” replacement for existing reporters, without the need to change any other aspect of a CRISPR-Cas12a-based assay. The reporter is readily available and employs a FRET pair to produce two signals upon cleavage by Cas12a. Use of both signals in a ratiometric manner provides for improved assay performance and a decreased time-to-result for several CRISPR-Cas12a assays. We comprehensively characterize this reporter to better understand the reasons for the improved signaling capacity and benchmark it against the current standard CRISPR-Cas reporter. Finally, to showcase the real-world utility of our reporter, we apply it to the analysis of Human papillomavirus in clinical sample
Synergizing data-driven and knowledge-based hybrid models for ionic separations
No full textA hybrid modeling framework has been developed for electrodialysis (ED) and resin-wafer electrodeionization (EDI) in brackish water desalination, integrating compositional modeling with machine learning techniques. Initially, a physics-based compositional model is utilized to characterize the behavior of the unit. Synthetic data is then generated to train a machine learning-based surrogate model capable of handling multiple outputs. This model is further refined using a limited set of experimental data. The effectiveness of this approach is demonstrated by its ability to accurately predict experimental results, indicating a faithful representation of the system\u27s behavior. Through analysis of feature importance facilitated by the machine learning model, a nuanced understanding of the interaction between the chosen ion-exchange resin wafer type and ED/EDI operational parameters is obtained. Notably, it is found that the applied cell voltage has a predominant impact on both separation efficiency and energy consumption. By employing multi-objective optimization techniques, experimental conditions are identified that achieve 99% separation efficiency while keeping energy consumption below 1 kWh/kg
One-Step Mechanochemical Synthesis of Bulk Sized Electroactive MoS2/Oxalic Acid Dihydrate Composite for Catalytic Nitrophenol Reductions
No full textNitrophenols are used in fabricating explosives and reported to be carcinogenic in nature, dictating a necessity for its efficient and eco-friendly reduction. Majority of such reductions involve multistep protocols and use expensive reagents and catalysts involving Au, Ag and Re. In this work, a one-step greener approach has been realized to mechanochemically prepare a cost-effective molybdenum disulfide (MoS2) and oxalic acid dihydrate composite for the catalytic reduction of nitrophenols into their corresponding amine in aqueous medium. The catalyst is bulk sized and works in-situ by virtue of the electroactivation of the morphologically rough MoS2 surface with nascent active sites. Such active sites are different from the conventional defect based active sites since these are composed of paramagnetic Mo5+ centers. These paramagnetic centers are generated during the mechanical grinding process and get exposed to the reactant at the outset of the reduction providing alternative reduction pathways. The epitactically transformed oxalic acid dihydrate which is physisorbed on the MoS2 surface during the catalyst’s preparation process, gets released in aqueous medium lowering the pH and accelerating the hydrolysis of BH4- . The BH4- quickly interacts with the nascent active sites propagating the reduction at a faster rate. We establish an Eley-Rideal mechanism that obeys first-order kinetics with a remarkable rate constant. These findings are based on thorough analysis using UV-visible spec-troscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman and electron paramagnetic resonance spectrosco-pies, high-resolution mass spectrometry along with first-principles quantum mechanical solid-state calculations
Simulations of photoinduced processes with the exact factorization: State of the art and perspectives
No full textThis Perspective offers an overview on the applications of the exact factorization of the electron-nuclear wavefunction to the domain of theoretical photochemistry, where the aim is to gain insights into the ultrafast dynamics of molecular systems via simulations of their excited-state dynamics beyond the Born-Oppenheimer approximation. The exact fac- torization offers an alternative viewpoint to the Born-Huang representation for the interpretation of dynamical processes involving the electronic ground and excited states as well as their nonadiabatic coupling through the nuclear motion. Therefore, the formalism has been used to derive algorithms for quantum molecular-dynamics simulations where the nuclear motion is treated using trajectories and the electrons are treated quantum mechanically. These algorithms have the characteristic features of being based on coupled and on auxiliary trajectories, and have shown excellent perfor- mance in describing a variety of excited-state processes, as this Perspective illustrates. We conclude with a discussion on the authors’ point of view on the future of the exact factorization
Encoding Circularity in Polydiketoenamine Thermoplastics via Oxy-Functionalization
No full textHere, we show that oxy-functionalization at specific sites along polydiketoenamine (PDK) backbones affects depolymerization rates by over three orders of magnitude, due to differences in distortion energies associated with reactive chain conformations in transition states for acidolysis. Site-specific oxy-functionalization, resulting in the fastest rates of acidolysis, opens the door to deconstructing linear PDK chain topologies for the first time, broadening the scope of applications for PDK plastics in a circular manufacturing economy, including chemically recyclable adhesives for a diverse range of surfaces
Enhancing Nanozyme-Based Colorimetric Assays by Optimizing Substrate Composition
No full textNanozymes, while promising alternatives to natural peroxidases in colorimetric assays, are often hindered by lower catalytic efficiencies. While various strategies exist to enhance signal intensity in nanozyme-based assays, substrate optimization remains largely underexplored. The vast majority of studies rely on standard sodium acetate buffers or commercially-sourced substrates optimized for horseradish peroxidase, neglecting the unique catalytic properties of different nanozymes. This work presents a systematic optimization of 3,3\u27,5,5\u27-tetramethylbenzidine (TMB)-based substrate compositions for four common nanozymes: iron oxide, LaNiO3, Mn-doped CeO2, and platinum nanoparticles. Our findings reveal that while sodium acetate buffer is suitable for LaNiO3, alternative buffers significantly enhance signal intensity (41-68%) for the other nanozymes. Further optimization of ionic strength, organic co-solvent type and concentration, and TMB/H2O2 concentrations yielded improvements in signal intensity, analytical sensitivity, and assay time. This study also identifies common pitfalls encountered during substrate optimization and proposes potential solutions. We posit that substrate composition should be a standard optimization step in the development of nanozyme-based assays, and the use of commercially-sourced substrates with undisclosed compositions should be avoided
Non-hydrolytic sol-gel synthesis of amine-functionalized silica: Template- and catalyst-free preparation of mesoporous catalysts for CO2 valorization
No full textCarbon dioxide utilization presents an important and topical research topic. However, the performance of catalysts needed for CO2 transformations does not achieve the necessary levels for their widespread application. To this end, we decided to study non-aqueous condensations providing amine-functionalized silica catalysts, possibly active in CO2-epoxide cycloaddition reaction. While non-hydrolytic sol-gel method is well-known for its efficiency in providing highly porous Lewis and Brønsted acid metallosilicates, here we show for the first time its application for the preparation of silica-based catalysts containing basic groups. First, the reaction conditions were screened to reproducibly obtain porous materials with preserved amine moieties. These were identified as follows: silicon tetraacetate and bridging tertiary amine silanes as precursors, toluene as a solvent, and temperature between 160 and 180 °C. In such a way, materials with up to 776 m2 g−1 and 1.58 cm3 g−1 were obtained in one-step process, without any template, after conventional drying step. Next, the amine-functionalized materials were tested in CO2-epoxide coupling providing cyclic organic carbonates with high selectivity (>99 %) and moderate activity (up to 86 % epichlorohydrin conversion after 1 h at 120 °C and 10 bar CO2). The characterization of spent catalysts revealed a presence of cyclic organic carbonates at the catalyst surface as well as conversion of tertiary amine groups to quaternary ammonium moieties
Zweifel Olefination for C-Glycosylation
No full textStarting from glycal derivatives, the Zweifel olefination presents an elegant opportunity to access C-glycosides in a selective manner. a-Lithiation of D-glucal, L-rhamnal, D-xylal and L-arabinal scaffolds was employed as a starting point in the synthesis of corresponding unsaturated aryl-, heteroaryl- and alkenyl-C-glycosides. This provides a straightforward strategy towards pharmacorelevant gliflozins and other unreported rhamnal- and xylal-analogs