Structure-property Relationships Research Articles

Controlling the optoelectronic properties of nitrogen-doped carbon quantum dots using biomass-derived precursors in a continuous flow system

The synthesis of carbon quantum dots (CQDs) from high molecular weight biomass-derived precursors poses a significant challenge due to the complex molecular structures and low conversion efficiency. This work demonstrates a green, rapid, and sustainable continuous hydrothermal flow synthesis (CHFS) approach for nitrogen-doped carbon quantum dots (NCQDs) from various biomass-derived precursors, including high molecular weight polymeric sources like chitosan, lignin, and humic acid. We find that the precursor structure significantly impacts the size of the fabricated NCQDs and their optical properties. Citric acid, a low molecular weight precursor, yields NCQDs with excitation-independent emission, higher quantum yields, and low non-radiative losses, while NCQDs derived from polymeric precursors exhibit excitation-dependent, red-shifted, and lower efficiency emission. Theoretical calculations, performed to understand the configuration and distribution of nitrogen dopants within the NCQD structure, show that pyridinic and graphitic nitrogen atoms exhibit a strong preference to aggregate near the centre of the edge of the NCQD and not in the vertices nor in the graphitic core, thus affecting the HOMO and LUMO, bandgap, and light absorption and emission wavelengths. The life cycle assessment (LCA) analysis highlights the green and scalable advantages of the CHFS process for producing NCQDs compared to batch methods, making it a sustainable and economically viable approach for large-scale NCQD synthesis from high molecular weight biomass-derived precursors. Hence, the combination of experimental data and theoretical calculations provides a comprehensive understanding of the structure-property relationships in these NCQDs.

Discovery Process Chemistry: An Innovation Hub at the Interface of Academia, the Pharmaceutical Industry, and Contract Research Organizations

AbstractDiscovery Process Chemistry (DPC) is an emerging intersectoral space that is characterized by the development of new chemical reactions or syntheses that enable the efficient elucidation of structure-activity relationships (SARs) and structure-property relationships (SPRs) as well as a rapid transition to process development. Drug discovery and development are accelerated by such efforts and this has led chemists in academia and industry alike to place an increasing importance on these aims. In this Short Review, we explore recent advances in DPC and the impact that it can have on SAR/SPR interrogation and downstream drug development efforts.1 Introduction2 Enabling SAR/SPR Interrogation with Bioisosteres3 Couplings of Diversifiable Reaction Partners4 Late-Stage Functionalization5 Conclusion and Outlook

Quantitative Structure Photovoltaic Properties Relationship of Coumarin Dyes Derived

The performance of an organic solar cell is strongly influenced by the structure of the photosensitizer. In this work, the open-circuit voltage (<I>V<SUB>OC</SUB></I>) and conversion efficiency (<i>η</i>) of a series of coumarin dyes are quantitatively related to the structure of nine coumarin derivatives. The Quantitative Structure Property Relationship (QSPR) is performed using the statistical method of multiple linear regression. In addition, descriptors determined from the ground state at the Cam_B3lyp/6-31G(d, p) level of theory and from the 2D structure of the molecules are mathematically related to the photovoltaic properties. These VOC and <i>η </i>models are accredited with very good statistical indicators (<I>R<sup>2</sup></I> = 0.906 and 0.918; Q<sub>cv</sub><sup>2</sup>= 0.845 and 0.849; S= 0.045 and 0.112; F = 14.524 and 16.846). These statistical indicators confirm the robustness and performance of the models developed. The results show that Voc improves with decreasing surface tension (<i>ts</i>) and increasing number of cycles (<i>cycle</i>). As for the conversion efficiency of light radiation into electrical energy, it is optimal when the light harvesting efficiency (<i>LHE<sub>th</sub></i>) and the excited state lifetime (<i>τ<sub>th</sub></i>) are high. In conclusion, these models have good predictive capabilities and can be used to predict and explain the open-circuit voltage and efficiency of coumarin derivatives that belong to the same field of application.

Molecule Empowerment and Crystal Desensitization: A Multilevel Structure-Property Analysis toward Designing High-Energy Low-Sensitivity Layered Energetic Materials.

Layered energetic materials (LEMs) can effectively balance energy and mechanical sensitivity, making them a current research focus in the field of energetic materials. However, the influence of the layered stacking pattern on impact sensitivity is still unclear, leading to the lack of advanced design strategies for high-energy low-sensitivity LEMs. Herein, we first utilize novel indicators such as maximum plane separation and hydrogen bond dimension to perform high-throughput screening on over 106 candidate structures, resulting in 17 target crystals. A systematic analysis was then conducted on the relationships between the bond dissociation energy (BDE) of the weakest energy-storing bond at the molecular level, the intralayer hydrogen bond energy (HBE), and the sliding energy barrier (SEB) at the crystal level with impact sensitivity. The findings suggest that a material can have low sensitivity only if at least two of the three properties perform well, and the interlayer sliding resistance can be reduced by enhancing the intermolecular hydrogen bond interactions, which reasonably explains the experimental phenomena. More importantly, we developed a prediction model for the impact sensitivity of LEMs with a coefficient of determination of 0.88. Additionally, factors affecting HBE and SEB were identified, and a linear model was established based on molecular-level feature variables. Finally, a new strategy for designing high-energy low-sensitivity LEMs was proposed, namely, empowerment at the molecular scale and desensitization at the crystal scale. This study integrates high-throughput screening, multilevel structure-property relationship analysis, and mathematical model construction, offering new perspectives for the development of novel high-energy and low-sensitivity energetic materials.

Learning grain boundary segregation behavior through fingerprinting complex atomic environments

Although continuum-scale segregation is a well-documented behavior in multi-species materials, detailed site-specific behavior remains largely unexplored. This is partially due to the complexity of analyzing materials at the requisite time and length scales for describing segregation with full atomic accuracy. Here, we better evaluate the segregation behavior of disordered grain boundary (GB) atomic environments through leveraging a set of Strain Functional Descriptors (SFDs) to generate an atomic descriptor (i.e., fingerprint). Using this atomic fingerprint, we resolve key relationships between atomic structure and segregation energy. Machine learning (ML) techniques are utilized in concert with this SFD fingerprint to elucidate complex relationships relating segregation potential to changes in specific features of the local Gaussian density captured by the SFDs. Finally, we identify relationships that indicate both individual and joint structure-property correlations. Linking atomic segregation energy to key structural features demonstrates the value of higher-order descriptors for uncovering complex structure-property relationships at an atomic scale.

Effect of Alkyl Chain Length on Room-Temperature Phosphorescent Probes for Mitochondria-Targeted Imaging.

Room temperature phosphorescent (RTP) probes have significant advantages in the field of cellular imaging, as their long lifetimes can prevent interference from the spontaneous fluorescence of organisms. Persulfurated arenes are a typical RTP molecular parent nucleus. However, most of the applied research on them is concentrated in anti-counterfeiting, and relatively few are applied in bioimaging. The molecular structure and structure-property relationship of them applied in bioimaging are still in the exploration stage. In this work, we have designed and synthesized a series of RTP probes with long alkyl chains, all of which can be targeted to mitochondria with good water solubility for mitochondria-targeted imaging. Further, we investigated the effect of alkyl chains on the luminescence properties of these probes, and found that the moderate length of alkyl chains can realize the enhancement of phosphorescence intensity. We believe this finding is of guiding significance for the design of molecular structures in the field of RTP probes.

Enhancing Two-Photon Excited Fluorescence of Metal-Organic Framework Single Crystals through Modulation of Inorganic Nodes.

Regulation of the two-photon excited fluorescence (TPEF) emission intensity and wavelength of metal-organic framework (MOF) crystals with similar constitutions presents a significant challenge. In this study, two MOFs, Zn-BTPPA and Cd3-BTPPA, were constructed using tetrakis(1,1'-biphenyl-4-carboxylic acid)-1,4-benzenediamine (H4BTPPA) as the organic ligand and mononuclear Zn and trinuclear Cd3 inorganic nodes, respectively. The incorporation of H4BTPPA within the MOF structures enables effective TPEF emission in both Zn-BTPPA and Cd3-BTPPA. The TPEF results show that Zn-BTPPA and Cd3-BTPPA exhibited strong emissions at 523 and 463 nm, respectively, when excited with a 780 nm laser. Moreover, Zn-BTPPA and Cd3-BTPPA exhibited much higher two-photon absorption cross sections, approximately 4.9 and 5.2 times higher than that of the reported dinuclear MOF, Cd2-BTPPA, with a similar composition, respectively. With different inorganic nodes, the stacking of chromophores, π···π interactions, and ligand geometry were found to correlate with the enhanced TPEF in Cd3-BTPPA and the blue-shifted TPEF in Zn-BTPPA. This work serves as an inspiration for designing efficient TPEF MOF materials based on the structure-property relationship.

Pressure‐Enhanced Superconductivity and Structural Phase Transition in Layered Sn4P3

High pressure provides a unique tuning method depending on structure modulation to explore the structure–property relationship. Herein, the pressure‐induced structural phase transformation and enhanced superconductivity in a layered binary phosphide Sn4P3 are reported. Comprehensive measurements using in situ synchrotron X‐Ray diffraction and Raman spectroscopy reveal a structural phase transition with mild distortion of SnP3 building blocks and interlayer shrinkage under high pressure. This differs from a conventional trigonal SnAs(P)3 to square SnAs(P)4 topotactic transition in SnAs(P)‐based compound. Through this structure reconstruction under high pressure, electron distribution has been reorganized and phonons have softened, facilitating a high superconducting temperature (Tc) value of 7.8 K at 34.9 GPa, which is almost six times higher than its ambient value. The study introduces a new transition route in layered SnAs/SnP‐based intermetallic materials and provides insight into the structural and electronic changes under high pressure for Sn4P3.

Impressive nonlinear optical response of π-conjugated, photoluminescent soft nanoparticles in polymer matrix

Nonlinear optical (NLO) materials are useful for applications varying from modulation of optical signals to cancer therapy. Besides inorganic crystals and organic molecules with defined structures, carbonized products have emerged as a new generation of materials showing good NLO properties. Due to the small sizes, the NLO performance of such materials mainly originates from nonlinear absorption. Obtaining a product with a high content of π-conjugated moiety is the key to improving the NLO performance. By using aldehydes bearing π units as the precursors, in this work we synthesized three polymeric nanoparticles (PNPs) through one-step pyrolysis, which also have large contents of π-conjugated structures. It was found that a larger size of π unit in the precursor led to a higher content as well as the size of the π-conjugated structure, which induced a bathochromic shift in the emission and an improved performance in the NLO response. When embedded in polymethylmethacrylate films, the products showed reverse saturable absorption (RSA) behavior with β up to 4.20 × 10−6 m W−1 and optical limit threshold down to 0.0012 J cm−2, which are comparable to those of metal-doped counterparts. This work gives deep insight on the structure-property relationship of the pyrolyzed products from π-conjugated small molecules, which is also useful for the preparation of task-specific carbon dots (CDs) or PNPs in future.

On the Sources of Discrepancies Between Grain Size Measurements

Accurate quantification of grain size in polycrystals is extraordinarily important for quality assurance and the development of structure-property relationships, as grain size affects nearly all engineering properties of structural alloys, from strength and fatigue life to corrosion resistance and thermal conductivity. Despite nearly a century of the existence of standards for measuring grain size, issues persist in obtaining consistent grain size measurements across several techniques. Of particular interest is comparing optical microscopy or scanning electron microscopy on an etched surface with mapping of crystal orientations using electron backscatter diffraction (EBSD). In this work, discrepancies between methods in the ASTM E 112 and ASTM E 2627 standards are explored through simulated measurements on synthetic microstructures. It is concluded that a small but systematic discrepancy exists between planimetric and lineal intercept-based approaches, and a new empirical relationship between the ASTM grain size number G and lineal intercepts is proposed.

Understanding the structure-property relationship of anhydride-cured epoxidized vegetable oils: Modeling and molecular dynamics simulation

The development of high-performance thermosetting resins derived from epoxidized vegetable oil (EVO) has received significant attention in terms of the development of low-carbon economies. In this work, the all-atomic cross-linked models of anhydride-cured EVO were constructed and five cross-linking pathways involving distinct cure reactions were considered in the modelling process. The evolution of the number of distinct cure reactions and reactive groups of the cross-linked network under each pathway were monitored. The effects of the type of cure reaction, cure reaction probability, epoxy functionality of monomer, molar ratio of anhydride to epoxy, and anhydride structure on mass density, gelation transition, bulk properties, thermal properties, and mechanical properties of EVO-based thermosets were investigated in detail. The results show that the network exhibited minor difference in cure reactions but apparent thermo-mechanical properties of the thermosets. Etherification of epoxy groups and dehydration condensation caused the unfavorable thermo-mechanical properties. The glass transition temperature (Tg) is most affected by the molar ratio of anhydride to epoxy; whereas the Young's modulus is sensitive to the epoxy functionality of monomer. It is expected that the current work provides deep insights into the network formation and performance development of anhydride-cured EVO thermosets.

Nonplanar Nanographene with a Large Conjugated π-Surface.

Conjugated π-surfaces are ubiquitous in molecules and materials. However, large π-surfaces up to a few nanometers in size are difficult to construct in an atomically precise manner. They tend to aggregate because of strong π-π interactions, resulting in notorious problems for both purification and spectroscopic investigations. Here, by contrast, we report the design, synthesis, and full characterizations of a nonplanar nanographene 1, which has a large, precise, and nonstacked π-surface. It is soluble in common organic solvents and allows for thorough investigations. The structure of 1, comprising 85 fused rings with an extended π-surface of 3 nm in size, is unambiguously confirmed by single-crystal X-ray diffraction. Unusual electronic structures, record-high near-infrared absorption, pronounced magnetic shielding, and ultrastrong heteromolecular van der Waals complexations are demonstrated, enabling us to establish a clear structure-property relationship, which has been elusive for decades. These results have broad implications for studying and understanding various phenomena and processes relevant to both discrete and interacting π-surfaces.

QSPR-based prediction model for the melting point of polycyclic aromatic hydrocarbons using MLR and ANN methods

The melting point is an important property that helps generate specific compounds with desired thermos-physical properties. Much work has been done applying quantitative structure-property relationships to improve the melting-point correlations, but they are unreliable. This gap might come from the melting point's sensitivity for small molecular variations and descriptors, which currently do not fully consider all factors determining melting behavior. In this work, we provide a QSPR model for predicting the melting point of a heterogeneous polycyclic aromatic hydrocarbons dataset. The model was generated using a robust hybrid linear approach (Genetic Algorithm-Multiple Linear Regression) and a nonlinear approach named Artificial Neural Network (ANN). Three descriptors were chosen to explain the influence of molecular weight and symmetry on melting point. The resulting QSPR model can model melting-point behavior with an RMSE of 34.88K, a coefficient correlation value of R²=0.887, and a prediction coefficient of Q²LOO= 0.863. This study reveals that the results produced by MLR were appropriate and served to predict melting points. However, compared to the results obtained by the ANN model, we conclude that the latter is more effective and better than the MLR model. Based on the results, our suggested model may be effective in predicting melting points, and the selected descriptors play essential roles in determining melting points.

Unraveling the Origin of Reverse Plasmonic Circular Dichroism from Discrete Bichiral Au Nanoparticles.

Bichiral plasmonic nanoparticles exhibited intriguing geometry-dependent circular dichroism (CD) reversal; however, the crucial factor that dominates the plasmonic CD is still unclear. Combined with CD spectroscopy and theoretical multipole analysis, we demonstrate that plasmonic CD originates from the excitation of electric quadrupolar plasmons. Moreover, a comparative study of two distinct quadrupolar modes reveals the correlation between the sign of the CD and the local geometric handedness at the plasmonic hotspots, thereby establishing a structure-property relationship in bichiral nanoparticles. The reverse CD is attributed to the opposite directions of the wavelength shift of the two plasmon modes upon changing the particle geometry. By finely tuning the size of bichiral nanoparticles, we can further reveal that the dependence of plasmonic CD on the electric quadrupolar plasmons. Our work sheds light on the physical origin of plasmonic CD and provides important guidelines for the design of chiral plasmonic nanoparticles toward chirality-dependent applications.

Long-Chain Molecular Crystals Antimony(III) Alkanethiolates Sb(SCnH2n+1)3 (n ≥ 12): Synthesis, Crystal and Electronic Structures, and Supramolecular Self-Assembly via Secondary Interactions.

Currently, there is not much success in solving the molecular and crystal structures of long-chain metal alkanethiolate complexes [M(SCnH2n+1)m] at the atomic level. Taking Sb(SC16H33)3 (1) as an example, we herein disclose the structural characteristics of long-chain trivalent antimony(III) alkanethiolates Sb(SCnH2n+1)3 (n ≥ 12) by single-crystal X-ray crystallography. Specifically, the Sb atom is three-coordinated by alkanethiolate ligands and a slightly distorted triangular pyramid SbS3 core is formed owing to the unique intramolecular stereochemistry of three alkyl chains, namely, two of them almost parallel aligning and the third chain extending alone around the SbS3 core. We further determine the conformation, spatial orientation and packing density of alkyl chains in 1 along with a comparison to those in other long-chain crystalline systems, and reveal the roles of intermolecular van der Waals and Sb···S secondary interactions in molecular self-assembly, which enables 1 to be a layer-structured molecular crystal with a monoclinic P21/c unit cell. The band structures and the atomic orbital contributions to the valence band maximum and conduction band minimum for 1 have also been evaluated by DFT calculations and rationally correlated with its optical absorption property. This study will help understand and discover new structures and structure-property relations of long-chain chemical systems.

Amphiphilic Nanogels as Versatile Stabilizers for Pickering Emulsions.

Pickering emulsions (PEs) are stabilized by particles at the water/oil interface and exhibit superior long-term stability compared to emulsions with molecular surfactants. Among colloidal stabilizers, nano/microgels facilitate emulsification and can introduce stimuli responsiveness. While increasing their hydrophobicity is connected to phase inversion from oil-in-water (O/W) to water-in-oil (W/O) emulsions, a predictive model to relate this phase inversion to the molecular structure of the nano/microgel network remains missing. Addressing this challenge, we developed a library of amphiphilic nanogels (ANGs) that enable adjusting their hydrophobicity while maintaining similar colloidal structures. This enabled us to systematically investigate the influence of network hydrophobicity on emulsion stabilization. We found that W/O emulsions are preferred with increasing ANG hydrophobicity, oil polarity, and oil/water ratio. For nonpolar oils, increasing emulsification temperature enabled the formation of W/O PEs that are metastable at room temperature. We connected this behavior to interfacial ANG adsorption kinetics and quantified ANG deformation and swelling in both phases via atomic force microscopy. Importantly, we developed a quantitative method to predict phase inversion by the difference in Flory-Huggins parameters between ANGs with water and oil (χwater - χoil). Overall, this study provides crucial structure-property relations to assist the design of nano/microgels for advanced PEs.

Micro‐Ring Morphology of Ag7NCs and Light‐Induced Reversible Interconversion of FCC Ag14NCs via Cu2+ ions‐Mediated Particle‐Assisted Reversible Interconversion

AbstractDespite the remarkable progress made on intercluster conversion in atomically precise metal nanoclusters (MNCs) and their self‐organization to develop microscopic molecular architecture with well‐defined size and shape, achieving light‐induced reversible structural transformation and the development of micro‐ring self‐assembly in MNCs have, so far, remained elusive. The present investigation touches on these two long‐standing quests by showcasing a new route, light‐induced Particle‐Assisted Reversible Interconversion (PARI) for the reversible transformation from Face Centered Cubic (FCC) Ag14NCs to Ag7NCs. Our studies reveal that the lack of plasmonic silver nanoparticles (AgNPs) in the system results in the formation of Ag7NCs with metallic kernels having centrosymmetric crystal packing. The molecular self‐organization of Ag7NCs through various non‐covalent interactions such as C−H⋅⋅⋅O, C−H⋅⋅⋅H−C, and C−H⋅⋅⋅π leads to the formation of micro‐ring morphology, a unique molecular architecture in MNCs. The in situ generated AgNPs due to the acceleration of the reaction kinetics by Cu2+ ions facilitate the growth of Ag14NCs with FCC metallic kernel. These two structural units of AgNCs show light‐induced reversible structural transformation which is also associated with the reversible tuning of their spectroscopic and morphological signatures. This PARI‐guided interconversion strategy put forward a most appropriate example of a structure–property relationship in MNCs.

Synthesis and quantitative structure–activity relationship of unsaturated fatty acid amide propyl dimethyl tertiary amines and their application in clean fracturing fluid thickener in low temperature environment

Solve the problem of freezing and blocking of clean fracturing fluid thickener during winter fracturing operations in the north, which is conducive to improving the efficiency of fracturing operations and oil and gas production rate. In this paper, four kinds of fatty acid amidopropyl dimethyl tertiary amine were successfully prepared and characterized with FT-IR and 1H NMR. Their acid values and Krafft temperature are discussed. The molecular structures of the four kinds of fatty acid amidopropyl dimethyl tertiary amine salts were optimized using Gaussian09 software, then their single point energies were calculated. A quantitative structure–property relationship (QSPR) model was established to predict Krafft temperature of the four kinds of fatty acid amidopropyl dimethyl tertiary amine salts. N-(3-(Dimethylamino)propyl)oleamide (PKO-O), (9Z,12Z)-N-(3-(dimethylamino)propyl)octadeca-9,12-dienamide (PKO-LO) were selected as the main agent. The optimal thickener formulation O1-8 and O2-1 were optimized by single factor experiment and orthogonal test respectively. O2-1 thickener has high low-temperature stability at −5 °C. The viscosity increase property, gel breaking property, rheological property, and viscoelasticity of the clean fracturing fluid obtained by cross-linking O1-8 with O2-1 thickener were evaluated and the properties of O1-8 thickener are better. The result shows that the O1-8 thickener basically meets the conditions of the winter fracturing construction site, and has more practical application significance.

Structure, Properties and Degradation of Self-Assembled Fibrinogen Nanofiber Scaffolds.

Self-assembled fibrinogen nanofibers are promising candidates for skin tissue engineering due to their biocompatibility and ability to mimic the native blood clot architecture. Here, we studied the structure-property relationship and degradation of rehydrated fibrinogen nanofibers prepared by salt-induced self-assembly, focusing on the effect of scaffold layering, cross-linking time and freeze-drying. Optimal fiber stability was achieved with cross-linking by formaldehyde (FA) vapor, while treatment with liquid aldehydes, genipin, EDC, and transglutaminase failed to preserve the nanofibrous architecture upon rehydration. Scaffold layering did not significantly influence the mechanical properties but changed the scaffold architecture, with bulk fiber scaffolds being more compact than layered scaffolds. Freeze-drying maintained the mechanical properties and interconnected pore network with average pore diameters around 20 μm, which will enhance the storage stability of self-assembled fibrinogen scaffolds. Varying cross-linking times altered the scaffold mechanics without affecting the swelling behavior, indicating that scaffold hydration can be controlled independently of the mechanical characteristics. Cross-linking times of 240 min increased scaffold stiffness and decreased elongation, while 30 min resulted in mechanical properties similar to native skin. Cross-linking for 120 min was found to reduce scaffold degradation by various enzymes in comparison to 60 min. Overall, after 35 days of incubation, plasmin and a combination of urokinase and plasminogen exhibited the strongest degradative effect, with nanofibers being more susceptible to enzymatic degradation than planar fibrinogen due to their higher specific surface area. Based on these results, self-assembled fibrinogen fiber scaffolds show great potential for future applications in soft tissue engineering that require controlled structure-function relationships and degradation characteristics.

Quantitative Characterization of RCA-Based DNA Hydrogels - Towards Rational Materials Design.

DNA hydrogels hold significant promise for biomedical applications and can be synthesized through enzymatic Rolling Circle Amplification (RCA). Due to the exploratory nature of this emerging field, standardized RCA protocols specifying the impact of reaction parameters are currently lacking. This study varied template sequences and reagent concentrations, evaluating RCA synthesis efficiency and hydrogel mechanical properties through quantitative PCR (qPCR) and indentation measurements, respectively. Primer concentration and stabilizing additives showed minimal impact on RCA efficiency, while changes in polymerase and nucleotide concentrations had a stronger effect. Concentration of the circular template exerted the greatest influence on RCA productivity. An exponential correlation between hydrogel viscosity and DNA amplicon concentration was observed, with nucleobase sequence significantly affecting both amplification efficiency and material properties, particularly through secondary structures. This study suggests that combining high-throughput experimental methods with structural folding prediction offers a viable approach for systematically establishing structure-property relationships, aiding the rational design of DNA hydrogel material systems.