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Failure of the DFT Ladder for the Fulminic Acid Challenge
No full textProperties of the historically pivotal fulminic acid (HCNO) molecule have been computed with a panoply of 473 density functionals of all varieties, providing a snapshot of the performance of contemporary density functional theory (DFT) for a challenging chemical system. Exhaustive tabulations and statistical analyses have been carried out for geometric parameters, vibrational frequencies, barriers to linearity, and the HCN–O dissociation energy. As the DFT ladder is climbed, only befuddlement ensues as to whether HCNO has a linear or bent equilibrium structure. The distinctive, extremely flat H–C–N bending potential of fulminic acid is almost universally misrepresented by the DFT functionals, which are thus incapable of solving quasilinear/quasibent issues of this molecule. High-ranking DFT functionals produce catastrophic errors in the HCN + O(3P) → HCNO reaction energy, and lower rungs emerge as the best performers for many of the bond distances and harmonic vibrational frequencies. This research shows that the current DFT zoo of approximations is incapable of yielding any consensus or convergence on the equilibrium structure, H–C–N bending frequencies, or enthalpy of formation of HCNO. Additional analyses are performed on the side effects of popular dispersion corrections on the covalently bonded properties and thermochemistry of HCNO
Exploring Halide Perovskite Nanocrystal Decomposition: Insight by In-Situ Electron Paramagnetic Resonance Spectroscopy
No full textZero-dimensional (0D) and three-dimensional (3D) halide perovskite nanocrystals (HP-NCs), owing to their unique optoelectronic properties, are extensively studied for photocatalytic activity. However, HPs are highly sensitive to light, humidity, and other environmental factors, which accelerate their decomposition. Understanding the decomposition process is crucial for gaining insights into how to stabilize HP-NCs. Here, we investigate the radical-driven decomposition process and dynamics of the 0D C4PbBr6 and 3D CsPbBr3 NCs under the influence of visible light and a polar solvent by electron paramagnetic resonance (EPR) spectroscopy. Our findings indicate that light accelerates radical formation over time, making the decomposition of HP-NCs a self-sustaining process. Upon illumination of the NCs, hydroperoxyl radicals are formed first, followed by unconventional Br, Cs, and Pb-related radicals, indicating the initiation of NC decomposition. The decomposition of CsPbBr¬3 NCs starts after 3 min of light exposure, while C4PbBr6 NCs take 18 min, indicating the greater stability of the latter. Additionally, we evaluated the photocatalytic activity of the HPs toward degrading organic dyes. The 3D CsPbBr3 NCs performed as superior photocatalysts compared to their 0D Cs4PbBr6 NCs counterparts. Yet, linking the results of EPR measurements with the photocatalytic efficacy suggests that the CsPbBr3 NCs undergo degradation during the photocatalytic process, thereby serving as a sacrificial agent to enhance photocatalytic activity. The understanding derived from EPR spectroscopy in tracking radical formation and dynamics can be extended to enhance the stability and efficiency of various nanomaterials in optoelectronic and photocatalytic applications, thus contributing to advancements beyond the HP family
A Percolating Path to Green Iron
No full textAbout 1.9 gigatonnes of steel is produced every year emitting 7\% (2.7 gigatonnes) of global CO in the process. More than 50\% of the CO emissions come from a single step of steelmaking, known as ironmaking. Hydrogen based direct reduction (HyDR) of iron oxide to iron has emerged as an emissions free ironmaking alternative. However multi-scale phenomena ranging from nanometers to meters inside HyDR reactors exhibit detrimental microstructure evolution which resists gaseous transport of H/HO, slows reaction rates and disrupts continuous reactor operation. To resolve the conundrum between atomic and reactor scales, we devise a percolation-theory model to reconcile nanoscale porosity with macroscopic properties relevant to reactor design models. Using synchrotron nano X-ray computed-tomography, we quantify the evolution of pores in iron oxide pellets, and demonstrate how nano-scale pore networks influence micro and macro-scale flow properties such as permeability, diffusivity and tortuosity. Our new modeling framework bridges the gap between scales and offers the criteria to accelerate HyDR by at least 5x via feedstock-reactor synergies based on percolation
Morphology determination of luminescent carbon nanotubes by analytical super-resolution microscopy approaches
No full textThe ability to determine the precise structure of nano-objects is essential for a multitude of applications. This is particularly true of single-walled carbon nanotubes (SWCNTs), which are produced as heterogeneous samples. Current techniques used for their characterization require sophisticated instrumentation, such as atomic force microscopy (AFM), or a compromise on accuracy. In this paper, we propose to use super-resolution microscopy (SRM) to accurately determine the morphology (orientation, length and shape) of individual luminescent SWCNTs. We generate super-resolved images using three recently published SRM analytical software packages (DPR, eSRRF and MSSR) and metrologically compare their performance to determine the morphological properties of SWCNTs. For this, ground-truth information on nanotube morphologies were obtained using polarization measurements and AFM to directly correlate the results from SRM at the single particle level. We show a more than 4-fold improvement in resolution over standard photoluminescence imaging, revealing hidden morphologies as efficiently as AFM. We finally demonstrate that DPR, and eventually eSRRF, can effectively assess SWCNT length distribution in a much faster and more accessible way than AFM. We believe that this approach can be generalized to other types of luminescent nanostructures and thus become a standard for rapid and accurate characterization of samples
Multiliter Scale Photosensitized Dimerization of Isoprene to Sustainable Aviation Fuel Precursors
No full textSynthetic routes to sustainable aviation fuels are needed to mitigate environmental impacts of the aviation sector. Among several emerging methods, the use of light-driven reactions benefits from milder conditions and the possibility of using sunlight to directly irradiate reactants, or alternatively, to power LEDs with a high and constant light intensity. Dinaphthylketone photosensitized dimerization of isoprene can afford C10-cycloalkenes that, after hydrogenation, meet the required properties for jet fuels (strongly resembling Jet-A). Isoprene can be photobiologically produced by metabolically engineered cyanobacteria from the conversion of CO2 and water by utilizing solar light, contributing to a carbon-neutral process. The scale-up of such a combined photobiological-photochemical route is essential to bring it closer to a commercial level. Herein, we present the optimization and scale-up of the photosensitized dimerization of isoprene. By designing different reactor setups, flow versus no-flow conditions and LED lamps (λmax = 365 nm) versus sunlight as the light source, we reached a 2.6 liter-scale able to produce 61 mL of isoprene dimers per hour, which represents a 14-fold higher productivity compared to our previous results at smaller scale. We also demonstrated a continuous feed process converting isoprene into dimers with a 95% yield under LED irradiation. These advancements highlight the potential of light-driven processes to contribute to the energy transition and production of sustainable aviation fuels, making them more viable for commercial use and significantly reducing the environmental impact of the aviation sector
Vulcanization accelerators and silica coupling agents in polyisoprene melts
No full textThe achievement of sufficient dispersion of vulcanization accelerators is critical to tailoring superior cross-linked elastomers. Modern recipes rely on multicomponent formulations with silica particles covered by coupling agents. We study the molecular properties of select accelerators in polyisoprene melts and their affinity for functionalized surfaces via extensive all-atom molecular dynamics simulations. We focus on the common (N-cyclohexyl)-2-benzothiazole sulfenamide (CBS), 1,6-Bis((dibenzylthiocarbamoyl)disulfanyl) hexane (DBTH) and diphenyl guanidine (DPG) molecules and their mixing characteristics at curing temperatures. Our results support a low association affinity for CBS and DBTH with polyisoprene, whereas DPG forms small hydrogen-bonded aggregates. Subsequently, we examine systems in contact with silica interfaces, bare or grafted with (3-Mercaptopropyl) triethoxysilane (MPTES), (3- Octanoylthio) 1-propyl-triethoxysilane (NXT), and bis (triethoxypropyl) disulfide (TESPD). Accelerator-substrate affinity is first assessed at infinite dilution using free energy calculations and subsequently at finite concentrations. Accelerators exhibit high substrate affinity (DPG >CBS >DBTH) irrespective of functionalization. However, coupling agents are able to displace from the surface a significant amount that increases with the grafting density and the size of the coupling agent. Finally, we investigate the behavior of DPG in binary DPG-CBS formulations, where the former can act as a covering agent that solubilizes CBS into the bulk polyme
Isothiocyanate Enabled Versatile Cyclizations of Phage Dis-played Peptides for the Discovery of Macrocyclic Binders
No full textCyclic peptides exhibit advantages in binding protein targets with high affinity and competency in inhibiting protein-protein interactions (PPIs). Cyclic peptide phage display with over a billion variants is an invaluable tool in drug discovery. However, achieving efficient peptide cyclization on phages remains a challenge due to the limited availability of reaction sites, which also restricts scaffold diversity. Here, we report an isothiocyanate-derived crosslinker featuring dual reactive groups: a bro-mide that covalently attaches to cysteine thiols, and a thiocyanogen that selectively forms a thiourea bridge with either the N-terminal amino group or ε-amines of lysine, depending on pH. This strategy enables pH-modulated cyclization, with head-to-side chain cyclization at pH 6.5 and side chain-to-side chain ligation at pH 9.5, simultaneously generating thiourea scaffolds. To demonstrate the versatility and biocompatibility of this approach, we constructed cyclic peptide libraries using both cy-clization methods and successfully selected binders for several targets, including Cyp D, TNF, MDM2, and Keap1, with disso-ciation constants (KD) ranging from micromolar to nanomolar. Given the broad pharmacological potential of the thiourea moiety, this phage display library opens new chemical space with high scaffold diversity and the integration of a proven pharmacophore for the development of cyclic peptide therapeutics
Novel Therapeutic Applications of Stem Cell-Derived Exosomes in Enhancing Neurological Regeneration and Repair
No full textExosome-based therapies have emerged as a promising frontier in the field of regenerative medicine, particularly for neural repair. Exosomes, which are microvesicles derived from mesenchymal stem cells (MSCs), neural stem cells (NSCs), and induced pluripotent stem cells (iPSCs), exhibit significant regenerative potential. This manuscript aims to explore the therapeutic prospects of exosome-based treatments in neural injury and neurodegenerative conditions. Recent advancements have deepened our understanding of exosome cargo, including microRNAs (miRNAs), proteins, and growth factors, which are critical to their regenerative capacity. Exosomes operate at various levels to support neuroprotection, enhance axonal growth, promote synaptic plasticity, and modulate immune responses. This paper further discusses the efficacy of exosome treatments, highlighting ongoing and recent clinical studies that investigate the therapeutic benefits of exosomes, particularly through intranasal and intravenous administration routes. Despite their potential, several challenges remain, notably in the large-scale production, distribution, and immune compatibility of exosome-based therapies. This review also addresses future directions for enhancing exosome targeting within neural tissues, with a focus on bioengineering strategies to improve treatment precision. While exosome therapies hold promise for addressing neurodegenerative diseases such as Alzheimer\u27s disease, Parkinson\u27s disease, and stroke, further research is needed before they can be fully integrated into clinical practice
Disintegration of water nanodroplet in oil: Impact of amphiphile self-assembly, surface heterogeneity, and protrusions
No full textAmphiphiles self-assemble around water-in-oil nanodroplets, increasing interfacial heterogeneity,
reducing droplet size, and stabilizing the system through microemulsion formation. We
present molecular dynamics simulations investigating how amphiphiles modulate the heterogeneity
and disintegration of water nanodroplets. Utilizing network theory-based sub-ensemble analysis and
curvature analysis, we characterize the amphiphile self-assembly process and the disintegration of
water nanodroplets into smaller daughter droplets. We detail the microscopic mechanism of water
transport from the water droplet to the oil phase, facilitated by the formation of sharp, finger-like
protrusions on the droplet surface. Our results demonstrate a direct correlation between the rate of
droplet disintegration and temperature-induced thermal fluctuations
Development of Absolute Quantification Methods for Digital Immunoassays: Theoretical Framework and Establishment of Droplet-Based Digital Immunoassay Techniques
No full textThis paper analyzes the current digital Immunoassays techniques and their theoretical foundations. Traditional single-molecule immunoassay models based on a single discrete Poisson distribution cannot explain or achieve absolute quantification in theory. Therefore, this paper interprets the process of target protein capture by magnetic beads in digital immunoassays as a Poisson distribution process, using the magnetic beads themselves as discrete objects to calculate microvolume (Vd). Then, it models the secondary sampling process using hypergeometric or multivariate hypergeometric distributions to achieve absolute quantification of the target proteins. The paper includes a simulated analysis of the entire process. Additionally, we introduce a droplet-based absolute quantification method using digital immunoassay, establishing two technical approaches: the bead-counting method and the external calibration method. These are compared with the Single Molecule immunoassay and the electrochemiluminescence Immunoassay method. Finally, the feasibility of the internal calibration method is discussed through simulation and modeling. The theories introduced in this paper can effectively solve the problem of absolute quantification in protein immunoassays, providing theoretical support for the establishment of precise protein quantification methods