Molecular Insights into Early Nuclei and Interfacial Mismatch during Vapor Deposition of Hybrid Perovskites on Titanium Dioxide Substrate

Theoretical understanding of the nucleus structures of hybrid perovskites, such as those of the prototypical methylammonium lead triiodide (MAPbI₃), can greatly improve the deposited thin film quality and the resulting optoelectronic device performance. In this paper, we report a systematic molecular dynamics simulation study on nucleation and interfacial mismatch during the vapor deposition of MAPbI₃ on the TiO₂ substrate under different ionic precursor (PbI₂ and MAI salts) compositions and temperatures. Despite significant anisotropic lattice mismatches, small defects are observed at the TiO₂/[MAI]⁰ interface due to intermediate electrostatic attractions between I and Ti atoms, while very strong electrostatic attractions between Pb and O atoms lead to significant defects at the TiO₂/[PbI₂]⁰ interface. From the vapor deposition simulations, we identify PbI₄^2– tetrahedra, PbI₅^3– pyramids, and PbI₆^4– octahedra as dominant polyhedral building blocks of early MAPbI₃ nuclei. Specifically, the PbI₅^3– pyramids dominate over other polyhedra and could be a good candidate for converting into PbI₆^4– octahedra upon further crystallization. We further identify early MAPbI₃ nuclei built upon well-connected PbI_<i>x</i> polyhedral clusters and finally locate the efficient early MAPbI₃ nuclei based on sufficient amounts of surrounding MA⁺ cations. The populations of these early nuclei increase rapidly with increasing the MAI composition, suggesting that potential improvements in film quality could be introduced by depositing more MAI salts or MA⁺ cations, a finding consistent with experiments. Although the impact from temperature is weaker than that from composition, the optimal temperature for nucleation is found to decrease with increasing the precursor composition PbI₂/MAI. Finally, the TiO₂ substrate leads to layered structures of ionic species close to its surface, but such ordering does not seem to promote prenucleation, which poses a need for the new design of substrates that are more compatible with PbI₆^4–-based early nuclei

Reactive Molecular Dynamics Simulations of Biomass Pyrolysis and Combustion under Various Oxidative and Humidity Environments

Biomass, as a renewable carbon neutral energy source with abundant reserves, is a good candidate for future energy supplies. In this paper, a simplified biomass model composed of cellulose, hemicellulose, and lignin, described by a carefully selected reactive force field (ReaxFF), is investigated using molecular dynamics (MD) simulations. The pyrolysis and combustion processes of the biomass under different temperatures and oxidative and humidity conditions, are studied. We find that the individual products from the pyrolysis of the three biomass components are similar, including H₂O, H₂, CO, CO₂, and small organic molecules. The calculated activation energies for C–C bond dissociation are 34.53, 26.08, and 16.23 kJ mol^–1, respectively, for cellulose, hemicellulose, and lignin, consistent with the trend in experiments. Interestingly, light tar (C5–13) production reaches a maximum under intermediate temperatures, which could be further explored to optimize the production of light tar as liquid fuels. Compared to biomass pyrolysis in vacuum, hydrothermal treatment makes the C–C bonds more difficult to dissociate, but C–O bonds more vulnerable due to stronger attacks from ·H radicals. Higher H₂ concentration is produced under the H₂O atmosphere, while more CO is formed under the mixed H₂O/O₂ atmosphere. During biomass combustion, CO₂ mainly comes from the cracking and reforming of ·COOH and ·CHO radical groups or directly from CO oxidation. We also observe that during biomass combustion, the formation of CO is facilitated at higher temperatures, whereas CO₂ production is favored at lower temperatures. More rapid decomposition and oxidation of biomass during combustion occur under fuel-lean conditions compared to fuel-rich conditions. Finally, more H₂O and fewer H₂ molecules are generated during the combustion process under the O₂/CO₂ atmosphere when increasing the concentration of CO₂. On the basis of this theoretical study, a better understanding of the radicals, intermediates, products, and reaction kinetics involved in biomass pyrolysis and combustion could be achieved

Molecular Gibbs Surface Excess and CO₂‑Hydrate Density Determine the Strong Temperature- and Pressure-Dependent Supercritical CO₂–Brine Interfacial Tension

In CO₂ geological storage, the interfacial tension (IFT) between supercritical CO₂ and brine is critical for the storage capacitance design to prevent CO₂ leakage. IFT relies not only on the interfacial molecule properties but also on the environmental conditions at different storage sites. In this paper, supercritical CO₂–NaCl solution systems are modeled at 343–373 K and 6–35 MPa under the salinity of 1.89 mol/L using molecular dynamics simulations. After computing and comparing the molecular density profile across the interface, the atomic radial distribution function, the molecular orientation distribution, the molecular Gibbs surface excess (derived from the molecular density profile), and the CO₂-hydrate number density under the above environmental conditions, we confirm that only the molecular Gibbs surface excess of CO₂ molecules and the CO₂-hydrate number density correlate strongly with the temperature- and pressure-dependent IFTs. We also compute the populations of two distinct CO₂-hydrate structures (T-type and H-type) and attribute the observed dependence of IFTs to the dominance of the more stable, surfactant-like T-type CO₂-hydrates at the interface. On the basis of these new molecular mechanisms behind IFT variations, this study could guide the rational design of suitable injecting environmental pressure and temperature conditions. We believe that the above two molecular-level metrics (Gibbs surface excess and hydrate number density) are of great fundamental importance for understanding the supercritical CO₂–water interface and engineering applications in geological CO₂ storage

Ionic Effects on Supercritical CO₂–Brine Interfacial Tensions: Molecular Dynamics Simulations and a Universal Correlation with Ionic Strength, Temperature, and Pressure

For geological CO₂ storage in deep saline aquifers, the interfacial tension (IFT) between supercritical CO₂ and brine is critical for the storage security and design of the storage capacitance. However, currently, no predictive model exists to determine the IFT of supercritical CO₂ against complex electrolyte solutions involving various mixed salt species at different concentrations and compositions. In this paper, we use molecular dynamics (MD) simulations to investigate the effect of salt ions on the incremental IFT at the supercritical CO₂–brine interface with respect to that at the reference supercritical CO₂–water interface. Supercritical CO₂–NaCl solution, CO₂–CaCl₂ solution and CO₂-(NaCl+CaCl₂) mixed solution systems are simulated at 343 K and 20 MPa under different salinities and salt compositions. We find that the valence of the cations is the primary contributor to the variation in IFT, while the Lennard-Jones potentials for the cations pose a smaller impact on the IFT. Interestingly, the incremental IFT exhibits a general linear correlation with the ionic strength in the above three electrolyte systems, and the slopes are almost identical and independent of the solution types. Based on this finding, a universal predictive formula for IFTs of CO₂–complex electrolyte solution systems is established, as a function of ionic strength, temperature, and pressure. The predicted IFTs using the established formula agree perfectly (with a high statistical confidence level of ∼96%) with a wide range of experimental data for CO₂ interfacing with different electrolyte solutions, such as those involving MgCl₂ and Na₂SO₄. This work provides an efficient and accurate route to directly predict IFTs in supercritical CO₂–complex electrolyte solution systems for practical engineering applications, such as geological CO₂ sequestration in deep saline aquifers and other interfacial systems involving complex electrolyte solutions

Non-Invasive <i>In Vivo</i> Imaging of Near Infrared-labeled Transferrin in Breast Cancer Cells and Tumors Using Fluorescence Lifetime FRET

<div><p>The conjugation of anti-cancer drugs to endogenous ligands has proven to be an effective strategy to enhance their pharmacological selectivity and delivery towards neoplasic tissues. Since cell proliferation has a strong requirement for iron, cancer cells express high levels of transferrin receptors (TfnR), making its ligand, transferrin (Tfn), of great interest as a delivery agent for therapeutics. However, a critical gap exists in the ability to non-invasively determine whether drugs conjugated to Tfn are internalized into target cells <i>in vivo</i>. Due to the enhanced permeability and retention (EPR) effect, it remains unknown whether these Tfn-conjugated drugs are specifically internalized into cancer cells or are localized non-specifically as a result of a generalized accumulation of macromolecules near tumors. By exploiting the dimeric nature of the TfnR that binds two molecules of Tfn in close proximity, we utilized a Förster Resonance Energy Transfer (FRET) based technique that can discriminate bound and internalized Tfn from free, soluble Tfn. In order to non-invasively visualize intracellular amounts of Tfn in tumors through live animal tissues, we developed a novel near infrared (NIR) fluorescence lifetime FRET imaging technique that uses an active wide-field time gated illumination platform. In summary, we report that the NIR fluorescence lifetime FRET technique is capable of non-invasively detecting bound and internalized forms of Tfn in cancer cells and tumors within a live small animal model, and that our results are quantitatively consistent when compared to well-established intensity-based FRET microscopy methods used in <i>in vitro</i> experiments.</p></div

DataSheet1_Comprehensive pan-cancer analysis and the regulatory mechanism of AURKA, a gene associated with prognosis of ferroptosis of adrenal cortical carcinoma in the tumor micro-environment.ZIP

Background: The only curative option for patients with locally or locally advanced adrenocortical carcinoma is primary tumor curative sexual resection (ACC). However, overall survival remains low, with most deaths occurring within the first 2 years following surgery. The 5-year survival rate after surgery is less than 30%. As a result, more accurate prognosis-related predictive biomarkers must be investigated urgently to detect patients’ disease status after surgery.Methods: Data from FerrDb were obtained to identify ferroptosis-related genes, and ACC gene expression profiles were collected from the GEO database to find differentially expressed ACC ferroptosis-related genes using differential expression analysis. The DEFGs were subjected to Gene Ontology gene enrichment analysis and KEGG signaling pathway enrichment analysis. PPI network building and predictive analysis were used to filter core genes. The expression of critical genes in ACC pathological stage and pan-cancer was then investigated. In recent years, immune-related factors, DNA repair genes, and methyltransferase genes have been employed in diagnosing and prognosis of different malignancies. Cancer cells are mutated due to DNA repair genes, and highly expressed DNA repair genes promote cancer. Dysregulation of methyltransferase genes and Immune-related factors, which are shown to be significantly expressed in numerous malignancies, also plays a crucial role in cancer. As a result, we investigated the relationship of AURKA with immunological checkpoints, DNA repair genes, and methyltransferases in pan-cancer.Result: The DEGs found in the GEO database were crossed with ferroptosis-related genes, yielding 42 differentially expressed ferroptosis-related genes. Six of these 42 genes, particularly AURKA, are linked to the prognosis of ACC. AURKA expression was significantly correlated with poor prognosis in patients with multiple cancers, and there was a significant positive correlation with Th2 cells. Furthermore, AURKA expression was positively associated with tumor immune infiltration in Lung adenocarcinoma (LUAD), Liver hepatocellular carcinoma (LIHC), Sarcoma (SARC), Esophageal carcinoma (ESCA), and Stomach adenocarcinoma (STAD), but negatively correlated with the immune score, matrix score, and calculated score in these tumors. Further investigation into the relationship between AURKA expression and immune examination gene expression revealed that AURKA could control the tumor-resistant pattern in most tumors by regulating the expression level of specific immune examination genes.Conclusion: AURKA may be an independent prognostic marker for predicting ACC patient prognosis. AURKA may play an essential role in the tumor microenvironment and tumor immunity, according to a pan-cancer analysis, and it has the potential to be a predictive biomarker for multiple cancers.</p

NIR fluorescence lifetime FRET of TfnR-Tfn complexes in normal vs. cancer cells using time-domain, wide-field macroscopic imaging <i>in vitro.</i>

<p>Fluorescence lifetime analysis of TfnR-Tfn complexes using NIR FRET pair AF700–AF750 and a time-domain, wide-field macroscopic imaging system. (A) T47D (left panels) and HMECs (right panels) were internalized with AF700-Tfn (donor) or AF750-Tfn (acceptor) in increasing A:D ratios of 0∶1, 1∶4, 1∶3, 1∶2, 1∶1, 2∶1, and 3∶1 in a 96-well format. The first column on the left indicates the pixel intensity (PI) of donor fluorophores (AF700-Tfn) and the subsequent decrease in intensity as the ratio of acceptor molecules (AF750-Tfn) increase due to quenching. Short component lifetimes (SL) measured in picoseconds (ps) are shown in the second column, indicating a high sensitivity and uniform detection despite the heterogeneity of donor intensities in the sample (Table S3 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>). The columns on the left indicate the relative abundance of NFD populations and FD populations. Each image shows 20×20 pixels with 0.5 mm/pixel size. (B) Quantification of donors participating in FRET events are shown as %FD and show a positive relationship relative to increasing proportion of acceptor molecules in both T47D and HMECs (Table S4 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>). (C) The %FD in relation to acceptor levels show an independent relationship as seen in FRET results using visible FRET detected by confocal microscopy (Table S5 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>). (D) Sensitivity of FD% is consistent across 1×10⁵ to 1×10⁴ cells (Table S6 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>). PI = pixel intensity, SL = short lifetime, NFD% = non-FRET Donor%, FD% = FRET Donor%. Error bars indicate standard deviation.</p

Electrostatically Tuned Microdomain Morphology and Phase-Dependent Ion Transport Anisotropy in Single-Ion Conducting Block Copolyelectrolytes

Block copolyelectrolytes are solid-state single-ion conductors which phase separate into ubiquitous microdomains to enable both high ion transference number and structural integrity. Ion transport in these charged block copolymers highly depends on the nanoscale microdomain morphology; however, the influence of electrostatic interactions on morphology and ion diffusion pathways in block copolyelectrolytes remains an obscure feature. In this paper, we systematically predict the phase diagram and morphology of diblock copolyelectrolytes using a modified dissipative particle dynamics simulation framework, considering both explicit electrostatic interactions and ion diffusion dynamics. Various experimentally controllable conditions are considered here, including block volume fraction, Flory–Huggins parameter, block charge fraction or ion concentration, and dielectric constant. Boundaries for microphase transitions are identified based on the computed structure factors, mimicking small-angle X-ray scattering patterns. Furthermore, we develop a novel “diffusivity tensor” approach to predict the degree of anisotropy in ion diffusivity along the principal microdomain orientations, which leads to high-throughput mapping of phase-dependent ion transport properties. Inclusion of ions leads to a significant leftward and upward shift of the phase diagram due to ion-induced excluded volume, increased entropy of mixing, and reduced interfacial tension between dissimilar blocks. Interestingly, we discover that the inverse topology gyroid and cylindrical phases are ideal candidates for solid-state electrolytes in metal-ion batteries. These inverse phases exhibit an optimal combination of high ion conductivity, well-percolated diffusion pathways, and mechanical robustness. Finally, we find that higher dielectric constants can lead to higher ion diffusivity by reducing electrostatic cohesions between the charged block and counterions to facilitate ion diffusion across block microdomain interfaces. This work significantly expands the design space for emerging block copolyelectrolytes and motivates future efforts to explore inverse phases to avoid engineering hurdles of aligning microdomains or removing grain boundaries

Accuracy of fluorescence lifetime FRET using NIR fluorophores <i>in vivo.</i>

<p>Decreased fluorescence lifetime due to FRET is detectable through living mice. (A) Mice are injected with matrigel resuspended ∼1×10⁶ cells pre-internalized with Tfn conjugated with NIR dyes at A:D ratios of donor only, 1∶2, 1∶1, and 2∶1 and imaged. Images show donor intensities on the left column followed by measurements of the short lifetime component (Table S11 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>), which also shows uniformity. The NFD and FD species are shown on the following columns to the right. Each image shows 60×60 pixels with 0.5 mm/pixel size. (B) Quantification of the FD% shows a robust linear increase in proportion to an increasing amount of AF750-Tfn (acceptor). These results indicate that the macroscopic imaging system employed is capable of determining FRET-mediated lifetime changes of donor fluorophores in cells through living animal tissues. Error bars indicate standard deviation.</p

NIR fluorescence lifetime FRET of TfnR-Tfn complexes in normal vs. cancer cells using wide-field macroscopic imaging <i>in vivo.</i>

<p>Fluorescence lifetime FRET is detected between AF700-Tfn (donor) and AF750-Tfn (acceptor) in T47D cells within a live mouse. (A) Mice injected with ∼1.5×10⁶ T47D cells internalized with various ratios of NIR dyes conjugated to Tfn are shown. In the top two rows, donor AF700-Tfn is held constant at 40 µg/ml and imaged. Pixel intensity (PI) is shown on the first column on the left of the donor fluorophore. Short component lifetime (SL) of the donor dye (Table S7 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>) is uniform among a varied intensity of donor dye. The next two columns on the right show the population of non-FRET donor (NFD) and FRET-donor (FD), respectively, showing an increase upon introduction of the AF750-Tfn (acceptor). Similar results are shown with Tfn-AF700 (donor) at 20 µg/ml. Each image shows 60×60 pixels with 0.5 mm/pixel size. (B) Results of the FD% show similar results between the two amounts, and also showing similar increases in FD in relation to the addition of AF750-Tfn acceptor (Tables S8–S10 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080269#pone.0080269.s001" target="_blank">File S1</a>). Error bars indicate standard deviation. PI = pixel intensity, SL = short lifetime, NFD% = non-FRET Donor%, FD% = FRET Donor%.</p