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Spatial distribution and stability of Gd0.6Eu0.4VO4 nanoparticles injected in mouse ear pinnae
No full textX Ray Fluorescence XRF mapping is employed for the study of the spatial distribution of GdVO4 Eu nanoparticles NPs after their injection into mouse ear pinnae. The injected NP colloids were detectable in a concentration range from 5 to 30 mM in vanadate ions 90 530 nM in NP concentrations . The distribution maps were recorded separately for Gd, Eu, and V and reveal that the three elements are collocalized, indicating the NP stability after the injection. The distribution pattern of the NPs is not homogeneous; they follow bifurcated paths of easy flow demonstrating the complexity of the tissue colloid interactions. The V K, Gd L3 and Eu L3 edge X ray Absorption Fine Structure XAFS spectra of the NPs recorded prior to and after their injection confirm that the integrity of the nanoparticles is preserved after injection. This combined XRF XAFS analysis paves the way for studies on the long term fate of injected Gd containing NPs in tissue
Assessment of fine tuned large language models for real world chemistry and material science applications
Get PDFThe current generation of large language models LLMs has limited chemical knowledge. Recently, it has been shown that these LLMs can learn and predict chemical properties through fine tuning. Using natural language to train machine learning models opens doors to a wider chemical audience, as field specific featurization techniques can be omitted. In this work, we explore the potential and limitations of this approach. We studied the performance of fine tuning three open source LLMs GPT J 6B, Llama 3.1 8B, and Mistral 7B for a range of different chemical questions. We benchmark their performances against traditional machine learning models and find that, in most cases, the fine tuning approach is superior for a simple classification problem. Depending on the size of the dataset and the type of questions, we also successfully address more sophisticated problems. The most important conclusions of this work are that, for all datasets considered, their conversion into an LLM fine tuning training set is straightforward and that fine tuning with even relatively small datasets leads to predictive models. These results suggest that the systematic use of LLMs to guide experiments and simulations will be a powerful technique in any research study, significantly reducing unnecessary experiments or computation
Using environment sensitive tetramethylated thiophene BODIPY fluorophores in DNA probes for studying effector induced conformational changes of protein DNA complexes
No full textThe LutR protein represses the transcription of genes encoding enzymes for the utilization of L lactate in Bacillus subtilis through binding to a specific DNA region. In this study, we employed oligonucleotide probes modified by viscosity sensitive tetramethylated thiophene BODIPY fluorophores to investigate the impact of selected metabolites on the LutR DNA complex. Our goal was to identify the effector molecule whose binding alters the protein DNA affinity, thereby enabling gene transcription. The designed DNA probes exhibited distinctive responses to the binding and release of the protein, characterized by significant alterations in fluorescence lifetime. Through this method, we have identified L lactate as the sole metabolite exerting a substantial modulating effect on the protein DNA interaction and thus confirmed its role as an effector molecule. Moreover, we showed that our approach was able to follow conformation changes affecting affinity, which were not captured by other methods commonly used to study the protein DNA interaction, such as electro mobility shift assays and florescence anisotropy binding studies. This work underlines the potential of environment sensitive fluorophore linked nucleotide modifications, i.e. dCTBdp, for studying the dynamics and subtle changes of protein DNA interaction
How Amino Acids Intercalate in CaFe Layered Double Hydroxides A Combined RIXS and NEXAFS Study
Get PDFTwo dimensional layered double hydroxides LDHs are ideal candidates for a large number of bio catalytic applications due to their flexible composition and easy to tailor properties. Functionality can be achieved by intercalation of amino acids as the basic units of peptides and proteins . To gain insight on the functionality, we apply resonant inelastic soft x ray scattering and near edge x ray absorption fine structure spectroscopy to CaFe LDH in its pristine form as well as intercalated with the amino acids proline and cysteine to probe the electronic structure and its changes upon intercalation. We observe the activation of pristine LDH defect states by soft x rays and their passivation by the intercalated molecules. The nitrogen at the amino amino is found to form C NH bonds and thus generating positive charge at the amino group, moving it away from the positively charged LDH layers. The carboxyl group in cysteine is deprotonated and thus in zwitterionic state after intercalation. This negative charge is used to compensate the positive layer charge. For intercalated proline the spectral signature of a protonated carboxyl group is observed, however, we find orbital overlap to defects at the layer surfaces indicating strong interaction with the carboxyl group
Electrons, Localization but no Hopping Disorder as Key for Understanding Charge Transport in Mesoporous Silicon
Get PDFThis article presents a unique study on the charge carrier transport in electrochemically anodized mesoporous silicon by combining macroscopic conductivity and thermopower measurements. Temperature dependent electrical conductivity measurements reveal a thermally activated transport in extended electronic states. An intrinsic variation of the thermal activation energies from sample to sample upon apparent identical synthesis conditions is discussed interms of microscopic disorder. In a detailed analysis of the activation energies, the existence of a disorder dependent mobility edge between localized and extended states in a band tail with exponential density of states becomes indispensable for understanding the microscopic transport mechanism. The observation of a Meyer Neldel compensation rule for the conductivity between different samples is a direct consequence of this mobility edge. Temperature dependent thermopower measurements provide further, stringent proof for disorder dominated transport in extended states above the mobility edge and dispel an alternative explanation attempt for the Meyer Neldel rule in meso porous silicon based on multiphonon absorption upon charge carrier transpor
Unveiling charge utilization mechanisms in ferroelectric for water splitting
Get PDFCharge separation is a critical process for achieving high photocatalytic efficiency, and ferroelectrics hold significant potential for facilitating effective charge separation. However, few studies have demonstrated substantial photocatalytic activity in these materials. In this study, we demonstrate that in ferroelectric PbTiO3, surface Ti vacancy defects near the positively polarized facets impede photocatalytic performance by trapping electrons and inducing their recombination. To tackle this issue, we selectively grew SrTiO3 nanolayers on the polarized facets PbTiO3, effectively mitigating interface Ti defects. This modification establishes a efficient electron transfer pathway at the interface between the positively polarized facets and the cocatalyst, extending the electron lifetime from 50 microseconds to themillisecond scale and significantly increasing electron participation in water splitting reactions. Consequently, the apparent quantum yield for overall water splitting achieves the highest values reported to date for ferroelectric photocatalytic materials. This work provides an effective strategy for designing advanced ferroelectric photocatalytic system
Simultaneous mapping of the ultrafast time and fluence dependence of the laser induced insulator to metal transition in magnetite
Get PDFPump probe methods are a ubiquitous tool in the field of ultrafast dynamic measurements. In recent years, x ray free electron laser experiments have gained importance due to their ability to probe with high chemical selectivity and at atomic length scales. Measurements are typically repeated many thousands of times to collect sufficient statistics and vary parameters like delay or fluence, necessitating that initial conditions are restored each time. An alternative is presented by experiments which measure the relevant parameters in a single shot. Here, we present a time to space mapping imaging scheme that enables us to record a range of delays and laser fluences in any single shot of the x ray probe. We demonstrate the use of this scheme by mapping the ultrafast dynamics of the optically induced insulator to metal Verwey transition in a magnetite thin film, probed by soft x ray resonant diffraction. By extrapolating our results toward the conditions found at x ray free electron lasers with higher photon energy, we demonstrate that the presented data could be recorded in a single sho
X ray magnetic circular dichroism
No full textX ray magnetic circular dichroism XMCD is the difference in X ray absorption between left and right circularly polarized light in magnetic materials. It is the X ray counterpart of the magneto optic effect for visible light, but shows a magnetic contrast up to three orders of magnitude higher. The exploration of XMCD using high flux, monochromatic and polarization variable synchrotron sources has advanced the understanding of magnetism and magnetic materials, in particular, when combined with spectral analysis based on powerful sum rules this enables the quantification of spin and orbital moments with elemental, even chemical, selectivity and high sensitivity. As an essential cornerstone of techniques to probe magnetic nanostructures and spin textures as well as their dynamics, XMCD has become an indispensable tool for the study of magnetism at the nanoscale and atomic scale. This Primer provides an overview of the principles and physics underlying XMCD, the experimental techniques used to measure it and its application to the study and understanding of fundamental and technologically relevant magnetic phenomen
Green Fabrication of Sulfonium Containing Bismuth Materials for High Sensitivity X Ray Detection
Get PDFOrganic inorganic hybrid materials based on lead and bismuth have recently been proposed as novel X and gamma ray detectors for medical imaging, non destructive testing, and security, due to their high atomic numbers and facile preparation compared to traditional materials like amorphous selenium and Cd Zn Te. However, challenges related to device operation, excessively high dark currents, and long term stability have delayed commercialization. Here, two novel semiconductors incorporating stable sulfonium cations are presented, [ CH3CH2 3S]6Bi8I30 and [ CH3CH2 3S]AgBiI5, synthesized via solvent free ball milling and fabricated into dense polycrystalline pellets using cold isostatic compression, two techniques that can easily be upscaled, for X ray detection application. The fabricated detectors exhibit exceptional sensitivities 14 100 15 190 C Gyair amp; 8722;1 cm amp; 8722;2 and low detection limits 90 nGyair s amp; 8722;1 for [ CH3CH2 3S]6Bi8I30 and 78 nGyair s amp; 8722;1 for [ CH3CH2 3S]AgBiI5 , far surpassing current commercial detectors. Notably, they maintain performance after 9 months of ambient storage. The findings highlight [ CH3CH2 3S]6Bi8I30 and [ CH3CH2 3S]AgBiI5 as scalable, cost effective and highly stable alternatives to traditional semiconductor materials, offering great potential as X ray detectors in medical and security application
Metal cross linking of helical oligoamide nanorods serves as platform for hierarchical nanofibers
Get PDFHelical amp; 946; oligoamides serve as versatile molecular building blocks with the unique ability to maintain stable helical fold and be functionalized by sequence modifications without affecting the folding ability. Fibrous head to tail self assembly of these building blocks provides a platform to develop complex nanomaterials. In this study, the metallosupramolecular structure formed by Cu II coordination of the Ac amp; 946;3A amp; 946;3V amp; 946;3S amp; 945;H amp; 946;3A amp; 946;3V amp; 946;3A 1 H oligoamide was characterized with spectroscopic, microscopic, and computational methods. Our findings demonstrate that the hybrid sequence leads to a complex helical structure combining a 13 helix on a 14 helix template, stabilized by bifurcated hydrogen bonds. We observe that the 1 H fibers form in solution, and that copper coordination increases the size of the colloidal structures. When deposited, a homogeneous two dimensional surface coating was produced, and based on our measurements we are able to propose a structure for the supramolecular framework. These results underline the utility of metallosupramolecular frameworks in bottom up nanofabrication and nanostructured surface coating