Principles Study Research Articles

Effective Coupling Model to Treat the Odd-Even Effect on the Current-Voltage Response of Saturated Linear Carbon Chains Single-Molecule Junctions.

The calculation of the electrical charge transport properties of alkanes C n H 2n S 2 with (n = 4-11) was performed to understand the odd-even effect on its current-voltage response. The extended molecule and broadband limit models were used to describe the molecular junction and covalent coupling with the electrodes. It was shown that among the participating molecular orbitals, HOMO and HOMO-1 are the ones with the most charge transport contribution. Moreover, the odd-even effect is caused by the alternation of the eigenvalues of some frontier orbitals as a function of the number of carbons, especially the HOMO that dominates the electrical transport. It could also be noted that when the current is analyzed outside the resonance, the relationship with the number of carbons exponentially decays, confirming the reports in the literature. To the best of our knowledge, a first principle study of the odd-even effect in symmetric systems composed by linear saturated carbon chains covalently coupled to electrodes has not been reported yet.

Ex vivo optical coherence tomography combined with near infrared targeted fluorescence: towards in-vivo esophageal cancer detection.

Early detection of (pre)malignant esophageal lesions is critical to improve esophageal cancer morbidity and mortality rates. In patients with advanced esophageal adenocarcinoma (EAC) who undergo neoadjuvant chemoradiation therapy, the efficacy of therapy could be optimized and unnecessary surgery prevented by the reliable assessment of residual tumors after therapy. Optical coherence tomography (OCT) provides structural images at a (sub)-cellular level and has the potential to visualize morphological changes in tissue. However, OCT lacks molecular imaging contrast, a feature that enables the study of biological processes at a cellular level and can enhance esophageal cancer diagnostic accuracy. We combined OCT with near-infrared fluorescence molecular imaging using fluorescently labelled antibodies (immuno-OCT). The main goal of this proof of principle study is to investigate the feasibility of immuno-OCT for esophageal cancer imaging. We aim to assess whether the sensitivity of our immuno-OCT device is sufficient to detect the tracer uptake using an imaging dose (∼100 times smaller than a dose with therapeutic effects) of a targeted fluorescent agent. The feasibility of immuno-OCT was demonstrated ex-vivo on dysplastic lesions resected from Barrett's patients and on esophageal specimens resected from patients with advanced EAC, who were respectively topically and intravenously administrated with the tracer bevacizumab-800CW. The detection sensitivity of our system (0.3 nM) is sufficient to detect increased tracer uptake with micrometer resolution using an imaging dose of labelled antibodies. Moreover, the absence of layered structures that are typical of normal esophageal tissue observed in OCT images of dysplastic/malignant esophageal lesions may further aid their detection. Based on our preliminary results, immuno-OCT could improve the detection of dysplastic esophageal lesions.

Effect of B and Hf doping on vacancy defects in AlCrMoNbZr high entropy alloy: A first principles study

The AlCrMoNbZr high entropy alloy (HEA) has potential applications as a high-performance cladding coating material. Here, we report the results about the vacancy defects in AlCrMoNbZr HEA using first-principle calculations. We have explored the variations in bulk and vacancy defect properties due to different local chemical environments in AlCrMoNbZr HEA with and without B/Hf doping, using both supercell and special quasi-random structures (SQS) techniques. Vacancy formation energy (VFE) is analyzed in accordance with the statistical distribution across three systems. The VFE exhibits a broad range of values and is characterized by a normal distribution. It is also significantly influenced by the type of doping atoms and the type of vacancy. Specifically, B doping substantially reduces the vacancy formation energy, thereby facilitating the formation of vacancies. Furthermore, the doping of B and Hf exerts a considerable impact on the formation of Zr vacancies (Zr_Vac) and Mo vacancies (Mo_Vac). In addition, Al vacancies (Al_Vac) are most readily formed in the AlCrMoNbZr HEA, while Mo vacancies (Mo_Vac) are most easily formed following the introduction of B and Hf dopants. The VFE in AlCrMoNbZr HEA with and without Hf dopant increases with the increase of the number of Cr and Mo atoms in the local chemical environment, and decreases with the increase of the number of Zr atoms. In conclusion, B doping promotes the formation of vacancy, which is not conducive to the improvement of initial irradiation resistance performance. Fortunately, one can infer from the results of the effect of local chemical environment on VFE that it is rewarding in improving the initial irradiation resistance by increasing the occurrence of Mo–Mo and Zr–Zr arrangement in AlCrMoNbZr HEA.

Adsorption and sensing potential of tungsten (W) doped beta tellurene (β-Te) monolayer towards nitrogen oxides: A first principle study

Nitrogen oxides play a significant role in various biomedical conditions, including respiratory disorders, asthma, and cardiovascular problems, underscoring the urgent need for sensitive and selective devices in biomedical applications. This study offers a comprehensive analysis of the sensitivity of β-tellurene doped with 2.22 % tungsten to nitrogen oxides (NO, NO2, and N2O). Site-specific doping of tellurene with tungsten reduces the band gap and introduces magnetization in β-tellurene. The strong adsorption energies observed for NO, NO2, and N2O at site A (-2.45 eV, -2.39 eV, and -2.80 eV, respectively) suggest that W-doped β-Te monolayers are promising candidates for gas storage for these compounds. Conversely, weaker adsorption energies for the same gases at site B (-0.74 eV, -1.74 eV, and -0.09 eV) highlights the importance of doping location. The adsorption energy values at site B indicate that W-doped β-Te monolayers have potential as sensing materials for NO and as adsorbents for NO2 gas. Conversely, the weak adsorption energy for N2O at the B site demonstrates its non-interacting behaviour with the W-doped β-Te monolayer. Additionally, the negligible change in electronic properties and minimal charge transfer suggest that this configuration is unsuitable for N2O storage and sensing. The spin-resolved current-voltage characteristics of doped tellurene reveal distinct behaviors influenced by gas molecule adsorption. Overall, these findings underscore the potential of W-doped tellurene as a site-specific material for the adsorption and sensing of targeted gases.

First principles study of electronic structure of x-form phthalocyanine crystals doped with one-dimensional iodine atomic chains

The x-form phthalocyanine (Pc) crystal is composed of a square-lattice arrangement of one-dimensional and double-period molecular chains with molecular planes normal to the stacking direction, and doped iodine (I) atomic chains between these molecular chains are known to induce the insulator-metal transition. Using the van der Waals density functional method, we investigate the electronic structure of a single x-form silicon Pc (x-SiPc) chain and the x-SiPc crystal undoped and doped with I atomic chains in a comparative manner. Although a SiPc molecule has a Si pz derived orbital just above the LUMO, the aligned Si atoms in x-crystals, each of which is at the center of the molecular plane, dimerize in the stacking direction, which prevents formation of a Si metallic band. In a single SiPc chain, two molecules in each primitive unit cell are stacked face-to-face with a staggering angle of 45°. However, when these molecular chains aggregate to create x-crystals, the staggering angle deviates from 45° to about 40° to form H–H bonding orbitals like H2 molecules between neighboring molecular planes in the lateral direction. Doping of the I atomic chains converts half-filling of the doubly degenerate bands to a lower band occupancy, which corresponds to the insulator-metal transition observed experimentally. The equally spaced I atomic chains create a metallic band due to pz-orbital overlapping with an effective-mass ratio of 0.15. Although the SiPc chains operate to create equally spaced I atomic chains, the effect of I atoms trying to trimerize is larger. This trimerization prevents pz orbitals of I atoms from making a metallic band.

A first principles study of stability, electronic and thermoelectric characteristics of novel high temperature half- heusler alloys ScAgX (X=Si,Ge,Sn)

To meet the ever-increasing renewable energy demand Half- Heusler (HH) materials can be a potential candidate. Heusler materials are seeking popularity as efficient high-temperature thermoelectric materials. Here we systematically investigated the structural, electronic, mechanical and thermoelectric properties of novel HH compounds ScAgX (X = Si,Ge,Sn) in the framework of the first principles approach. These materials are found to be chemically, mechanically and dynamically stable. Born-Oppenheimer molecular dynamics simulations (BOMD) verify the thermal stability of these materials from 300 K to 1100 K. The semiconducting nature of these materials is confirmed by the electronic band structure. ScAgX (X = Si,Ge,Sn) have an indirect band gap of 0.37 eV, 0.42 eV and 0.38 eV respectively. A high value of Seebeck coefficient of 6351 μV/K, 6955 μV/K and 6558 μV/K has been obtained at room temperature. ScAgSi shows a high value of electrical conductivity (∼106 S/m) among these compounds at room temperature. The calculated value of the figure of merit (ZT) of ScAgX (X = Si,Ge,Sn) is 0.12, 0.08 and 0.16 at 1100 K respectively. Our present investigation shows that these materials can be a potential candidate for high-temperature thermoelectric power generation.

First principles study to investigate structural, optical properties and bandgap engineering of XSnI3(X=Rb, K, Tl, Cs) materials for solar cell applications

First principles study to investigate structural, optical properties and bandgap engineering of XSnI3(X=Rb, K, Tl, Cs) materials for solar cell applications

First principles study on electronic structure and optical property of O-doped lead-free perovskite CsSnCl3

First principles study on electronic structure and optical property of O-doped lead-free perovskite CsSnCl3

Design of microcomputer principle virtual experiment teaching platform and study on teaching mode

In view of the characteristics of "Microcomputer Principle and Interface Technology" experiment course, such as complex abstraction, easy damage of experimental instruments and poor reuse, this paper proposes to use virtual simulation technology to digitize the microcomputer principle experiment circuit and experiment process, so that students can complete the relevant experiment content on the virtual experiment platform. The virtual experiment platform provides students with an efficient, flexible, open and free experiment environment, enhances students' interest in experiment, improves experiment efficiency and experiment quality, and is of great help to improving students' independent innovation practice ability.

Evaluation of a new teaching-learning sequence on the particulate nature of matter using crystal structures

Although there has been extensive research on students’ understanding of the particulate nature of matter (PNM), there is still a lack of research on contexts that can be used to teach this challenging topic. In a previous design-based research study, the authors developed a teaching-learning sequence (TLS) on the PNM in the context of crystal structures based on 40 student interviews using the method of probing acceptance. Data suggested that salt and snow crystals form an effective context for learning the concept of emergence and therefore gaining a better understanding of the PNM. To test whether the TLS also promotes students’ use of the PNM in a realistic classroom setting, a proof of principle study was conducted. In six eighth-grade classes in Vienna, students’ use of the PNM was assessed with a pretest before they were taught the TLS during four lessons. After the intervention, students were given a post-test. Open-ended questions were coded using evaluative qualitative content analysis so that quantitative analysis could be applied. T-tests comparing the means of students’ scores on both tests show significant improvements in students’ use of the PNM in the post-test. The context of crystal structures seems to be helpful to students, as most of them use the PNM when asked about crystal formation. In addition, in the post-test, students more often accepted the idea of empty space between particles and associated particle motion with temperature. However, when asked about phase changes, most students remained in a continuous conception of matter. Published by the American Physical Society 2024

First Principle Study of the Relationship between Electronic Properties and Adsorption Energy: Xanthate Adsorption on Pyrite and Arsenopyrite

First Principle Study of the Relationship between Electronic Properties and Adsorption Energy: Xanthate Adsorption on Pyrite and Arsenopyrite

First principles study on the performance of Sn&F double-doped LiCoO2 in lithium-ion batteries

The demand for LIBs using LiCoO2 as a cathode material with higher energy density and improved safety is urgent. We have carried out a theoretical investigation of Sn&F double-doped LiCoO2 using first-principles calculations. The Sn&F double-doped LiCoO2 system, LiCo0.96Sn0.04O0.98F0.02, was modelled using a 3 × 3 × 1 supercell of LiCoO2 containing a pair of Co-O vacancies, with one O atom and one Co atom replaced by F and Sn, respectively. Our study shows that Sn&F doping contributes to a reduction in volume variation and inhibits Co migration during delithiation. Furthermore, Sn&F doping is shown to reduce the average activation barrier for Li diffusion.

Elemental Profiling for the Detection of Food Mixtures: A Proof of Principle Study on the Detection of Mixed Walnut Origins Using Measured and Calculated Data.

Element profiling is a powerful tool for detecting fraud related to claims of geographical origin. However, these methods must be continuously developed, as mixtures of different origins in particular offer great potential for adulteration. This study is a proof of principle to determine whether elemental profiling is suitable for detecting mixtures of the same food but from different origins and whether calculated data from walnut mixtures could help to reduce the measurement burden. The calculated data used in this study were generated based on measurements of authentic, unadulterated samples. Five different classification models and three regression models were applied in five different evaluation approaches to detect adulteration or even distinguish between adulteration levels (10% to 90%). To validate the method, 270 mixtures of walnuts from different origins were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Depending on the evaluation approach, different characteristics were observed in mixtures when comparing the calculated and measured data. Based on the measured data, it was possible to detect admixtures with an accuracy of 100%, even at low levels of adulteration (20%), depending on the country. However, calculated data can only contribute to the detection of adulterated walnut samples in exceptional cases.

Detection of pathogenic bacteria and biomarkers in lung specimens from cystic fibrosis patients

Diagnosing lung infections is often challenging because of the lack of a high-quality specimen from the diseased lung. Since persons with cystic fibrosis are subject to chronic lung infection, there is frequently a need for a lung specimen. In this small, proof of principle study, we determined that PneumoniaCheckTM, a non-invasive device that captures coughed droplets from the lung on a filter, might help meet this need. We obtained 10 PneumoniaCheckTM coughed specimens and 2 sputum specimens from adult CF patients hospitalized with an exacerbation of their illness. We detected amylase (upper respiratory tract) with an enzymatic assay, surfactant A (lower respiratory tract) with an immunoassay, pathogenic bacteria by PCR, and markers of inflammation by a Luminex multiplex immunoassay. The amylase and surfactant A levels suggested that 9/10 coughed specimens were from lower respiratory tract with minimal upper respiratory contamination. The PCR assays detected pathogenic bacteria in 7 of 9 specimens and multiplex Luminex assay detected a variety of cytokines or chemokines. These data indicate that the PneumoniaCheckTM coughed specimens can capture good quality lower respiratory tract specimens that have the potential to help in diagnosis, management and understanding of CF exacerbations and other lung disease.

First principles study on the mechanical properties and generalized stacking fault energy of CsCl, CsBr and CsI

First principles study on the mechanical properties and generalized stacking fault energy of CsCl, CsBr and CsI

Functionalized magnetic nanoparticles remove donor-specific antibodies (DSA) from patient blood in a first ex vivo proof of principle study

The presence of donor-specific antibodies (DSA) such as antibodies directed against donor class I human leucocyte antigen (e.g., HLA-A) is a major barrier to kidney transplant success. As a proof of concept, functionalized magnetic nanoparticles have been designed to eliminate DSA from saline, blood and plasma of healthy donors and sensitized patients. Specific HLA-A1 protein was covalently bound to functionalized cobalt nanoparticles (fNP), human serum albumin (HSA) as control. fNP were added to anti-HLA class I-spiked saline, spiked volunteers’ whole blood, and to whole blood and plasma of sensitized patients ex vivo. Anti-HLA-A1 antibody levels were determined with Luminex technology. Antibodies' median fluorescent intensity (MFI) was defined as the primary outcome. Furthermore, the impact of fNP treatment on blood coagulation and cellular uptake was determined. Treatment with fNP reduced MFI by 97 ± 2% and by 94 ± 4% (p < 0.001 and p = 0.001) in spiked saline and whole blood, respectively. In six known sensitized anti-HLA-A1 positive patients, a reduction of 65 ± 26% (p = 0.002) in plasma and 65 ± 33% (p = 0.012) in whole blood was achieved. No impact on coagulation was observed. A minimal number of nanoparticles was detected in peripheral mononuclear blood cells. The study demonstrates—in a first step—the feasibility of anti-HLA antibody removal using fNP. These pilot data might pave the way for a new personalized DSA removal technology in the future.

First principles study on toxic gas adsorption of PtSe2/GaN heterostructure modified by Cu-group elements

Monitoring and identifying toxic gases is essential due to their detrimental effects on human health and the environment. Consequently, developing high-efficiency sensors for the detection of these harmful gases is of paramount importance. Herein, we present a theoretical study on the adsorption and sensing properties of toxic gases CO, NO and NO2 on intrinsic and Cu, Ag and Au atom-decorated PtSe2/GaN van der Waals (vdW) heterostructures, based on first principles calculation investigations. The adsorption energy, charge transfer, band structures, density of states, charge density difference, electron localization functions and recovery time are analyzed. The findings reveal that the intrinsic system demonstrates weak adsorption capabilities. However, when the surface is modified with elements from the Cu-group, there is a significant improvement in the behavior related to gas adsorption. Particularly, the Ag-decorated system demonstrates optimal gas adsorption performance. Incorporating Ag atoms notably enhances the adsorption energy and the quantity of charge transfer for CO, NO and NO2, thereby promoting a shift from physical to chemical adsorption. This alteration significantly boosts the efficiency of adsorption processes for these gases. As for the recovery time, the decorated systems indicate potential application in gas detection devices and gas adsorbers at various temperatures.

Electron distribution regulating of nonmetal doped monolayer g-GaN for enhanced electrocatalytic CO2 reduction

Exploring inexpensive electrocatalysts that can efficiently and selectively convert CO2 into hydrocarbon fuels is important to promote carbon neutrality and solve the energy crisis. Current electrocatalysts, such as Cu-based alloys, single-atom catalysts, and dual-atom catalysts, use the d states of metal in the electrocatalytic CO2 reduction reaction. Inspired by this, this work studies CO2 reduction reaction from another approach. Herein, using first principles study, we systematically investigate the prospect of nonmetal (B, C, O and F) doped monolayers g-GaN as electrocatalysts for the CO2 reduction reaction. We found that nonmetal doping can effectively regulate the electron distribution and p-band center of the active center (N site), which can adjust the initial adsorption, activation degree, charge transfer amount of CO2, and promote the formation of intermediates. Interestingly, B and C doped systems have better catalytic activity for CH4, with limiting potentials of −0.61 and −0.53 V, respectively. More importantly, F doped system has higher activity and selectivity for CH3OH production and inhibit competitive HER, with lower limiting potentials of −0.60 V. This study provides a new theoretical basis for the design and screening of electrocatalysts with high activity and product selectivity using nonmetal as the active site.

The first principle study on the hydrogen storage properties of monolayer and bilayer α-graphyne decorated by alkali metal atoms

Using the first-principles density functional theory, the hydrogen storage properties of monolayer and bilayer α-graphyne systems decorated by alkali metal are investigated. The results of band structure and density of state analysis indicate that alkali metal decoration enhances the chemical activity of the adsorption substrate, leading to increased H2 adsorption capacities for Li, Na and K decorated monolayer systems (15.0 wt.%, 14.5 wt.%, 10.7 wt.%, respectively). The combined action of interlayer force and decorated metal atoms results in higher H2 adsorption capacities for Li, Na and K decorated bilayer systems (17.7 wt.%, 16.9 wt.%, 13.0 wt.%, respectively), which means the bilayer graphyne structures enhance the storage capacities for decorated structures. Additionally, the Na decorated rhombus bilayer system demonstrates the highest adsorption density of H2 molecules between α-graphyne layers. Overall, alkali metal decorated monolayer and bilayer systems exhibit promising H2 adsorption potentials.

First principle study of the CuCrTiS[formula omitted]: Spin-glass state and electronic transport

Magnetothermopower and giant magnetoresistance in spinel-type compound CuCrTiS4 has attracted a lot of attention recently. Ab initio computations of the electronic structure and the Seebeck coefficient of the CuCrTiS4 structure are reported. The mixed nature of magnetism was identified to be caused by the competition between ferromagnetic and anti-ferromagnetic impacts, with the corresponding determined exchanged parameters: J1=1.018 meV, J2=−5.59 meV, JL=0.22 meV. Seebeck coefficient and electrical conductivity of the CuCrTiS4 compound in the temperature range of 5−300 K along with its low temperature thermoelectric capabilities were calculated. The direct 0.4 eV band gap was determined by taking in account strong correlations effect via the Hubbard correction. The calculated Seebeck coefficient is in a good agreement with the available experimental data for a wide carriers concentrations range. This first detailed study of CuCrTiS4 reports that this thiospinel poses a mixed nature of magnetism along with unique thermoelectric properties.