PbS Systems Research Articles

Photoexcited Carrier Transfer in CuInS2 Nanocrystal Assembly by Suppressing Resonant-Energy Transfer.

High-density assemblies or superlattice structures composed of colloidal semiconductor nanocrystals have attracted attention as key materials for next-generation photoelectric conversion devices such as quantum-dot solar cells. In these nanocrystal solids, unique transport and optical phenomena occur due to quantum coupling of localized energy states, charge-carrier hopping, and electromagnetic interactions among closely arranged nanocrystals. In particular, the photoexcited carrier dynamics in nanocrystal solids is important because it significantly affects various device parameters. In this study, we report the photoexcited carrier dynamics in a solid film of CuInS2 nanocrystals, which is one of the potential nontoxic substitutes with Cd- and Pb-free compositions. Meanwhile, these subjects have been extensively studied in nanocrystal solids formed by CdSe and PbS systems. A carrier-hopping mechanism was confirmed using temperature-dependent photoluminescence spectroscopy, which yielded a typical value of the photoexcited carrier-transfer rate of (2.2±0.6)×107 s-1 by suppressing the influence of the excitation-energy transfer.

Theoretical calculation and experimental study on the separation mechanism of PbS-Sb2S3

Jamesonite (Pb4FeSb6S14) is a complex antimony sulfide mineral and an important raw material for the extraction of lead and antimony. Under vacuum conditions, the internal interaction mechanism of PbS and Sb2S3 during thermal decomposition is unclear and difficult to separate. In order to explore the interaction mechanism between PbS and Sb2S3, the thermodynamic data of Pb-S and Sb-S systems were firstly calculated by thermodynamic calculation method, PbS and Sb2S3 cluster substances that may exist in the gas phase were obtained under the given temperature conditions. On this basis, ab initio molecular dynamics was used to calculate the mean square displacement and diffusion coefficient of PbS and Sb2S3 gas phase clusters. The vacuum distillation experiments of lead sulfide and antimony trisulfide confirmed the volatilization and diffusion of PbS and Sb2S3, and verified the theoretical calculation results. According to the experiment, the volatilization temperature of Sb2S3 is much lower than that of PbS. The theoretical calculation results are consistent with the experimental results, which indicates that the calculation of the diffusion properties of PbS and Sb2S3 gas phase clusters by molecular dynamics simulation is reliable. This is also an effective and simple method to predict whether the mixed melt of PbS and Sb2S3 can be separated, which provides theoretical guidance for the vacuum separation of PbS and Sb2S3.

Insights into the Metabolic Response of Lactiplantibacillus plantarum CCFM1287 upon Patulin Exposure.

Patulin (PAT) is a common mycotoxin in the food industry, and is found in apple products in particular. Consumption of food or feed contaminated with PAT can cause acute or chronic toxicity in humans and animals. Lactiplantibacillus plantarum CCFM1287 is a probiotic strain that effectively degrades PAT in PBS and food systems. In this study, it was found that the concentration of PAT (50 mg/L) in MRS medium decreased by 85.09% during the first stages of CCFM1287 growth, and this change was consistent with the first-order degradation kinetic model. Meanwhile, the regulation of oxidative stress by L. plantarum CCFM1287 in response to PAT exposure and metabolic changes that occur during PAT degradation were investigated. The degree of intracellular damage was attenuated after 16 h of exposure compared to 8 h. Meanwhile, metabolomic data showed that 30 and 29 significantly different metabolites were screened intracellularly in the strain after 8 h and 16 h of PAT stress at 50 mg/L, respectively. The results of pathway enrichment analysis suggested that the purine metabolic pathway was significantly enriched at both 8 h and 16 h. However, as is consistent with the performance of the antioxidant system, the changes in Lactiplantibacillus diminished with increasing time of PAT exposure. Therefore, this study helps to further explain the mechanism of PAT degradation by L. plantarum CCFM1287.

Clinical Implementation of Lung SABR IMPT Using Two PBS Systems With Different Spot Sizes and Delivery Speeds

Stereotactic Ablative Body Therapy (SABR) is an effective treatment for early-stage lung cancer. Two different proton therapy delivery systems (Proteous-plus with universal nozzle called P+ and Proteus-one called P1) were employed to test the spot size difference, plan dosimetric quality, and delivery time needed for practical and effective clinical treatment.Total of 9 lung patients with 10 tumors were selected for this study. Seven targets were prescribed 60 Gy in 10 fractions; three patients were 48 Gy in 4 fractions. A treatment planning system was used to generate treatment plans for each nozzle type with exact same optimization objectives. P1 plans used 4cm range-shifter placed at 45cm from isocenter to create large in-air beam spots to mimic P+ system. The spot sizes were compared to the P+ in-air spots without range shifter. P+ plans used 7cm range-shifter placed very close to patients, i.e., 4cm away, to minimize spot size degradation. Target coverage was optimized and normalized to prescription dose cover 100-percent of GTV and 90-percent covers PTV. Dose to the OARs were compared using QUANTEC metrics. Each plan was split into three subsets to perform volumetric dose-repainting to reduce interplay effect. The plan beam-on times of both systems were obtained to evaluate treatment delivery efficiency and impact of patient comfort.The in-air beam spots were comparable between the P+ without and P1 with range shifter. All PTVs were covered by 90-percent prescription dose. OAR doses were comparable and within the QUANTEC limits. The beam-on time of P+ plans are 3 to 6 time of those of P1 plans. When combined with patient setup and image guidance, patient discomfort could lead to higher uncertainty in P+ treatment.P1 system with 45cm away from isocenter can effectively simulate a large spot PBS system, P+. Lung SABR IMPT plan qualities between the two systems were dosimetrically comparable. Volumetric dose-repainting were applicable to both systems to reduce interplay effect. However, the plan beam-on and delivery time of P1 system were significantly shorter than that of P+. Therefore, potential less patient movement during treatment leads to less dose uncertainties to patients.

Tuning electronic and magnetic properties of V-, Cr-, and Mn-doped PbS via strain engineering: A first-principles proposal

We theoretically investigated the possibilities of establishing ferromagnetism and tailoring band gap of narrow-gap PbS with early 3d transition-metals (V, Cr, and Mn) doping and strain engineering. The results revealed that these magnetic impurities can be spontaneously incorporated into PbS matrix. Moreover, V- and Mn-doped PbS materials are magnetic insulators, while Cr-doped PbS becomes nearly half metallic. When taking the spin-orbit coupling (SOC) effect into account, the strong p-d hybridization gives rise to the band gap closing for V- and Mn-doped PbS, creating two novel spin-gapless semiconductors. The induced gapless state could be further modulated by external strain, resulting in a topological phase transition with both gap opening and band inversion for V- and Mn-doped PbS systems. Particularly, we find that V-doped PbS is a ferromagnetic compound with intrinsic exchange field, which may be a potential candidate for the realization of quantum anomalous Hall effect.

MOCAT2: a metagenomic assembly, annotation and profiling framework.

Summary: MOCAT2 is a software pipeline for metagenomic sequence assembly and gene prediction with novel features for taxonomic and functional abundance profiling. The automated generation and efficient annotation of non-redundant reference catalogs by propagating pre-computed assignments from 18 databases covering various functional categories allows for fast and comprehensive functional characterization of metagenomes.Availability and Implementation: MOCAT2 is implemented in Perl 5 and Python 2.7, designed for 64-bit UNIX systems and offers support for high-performance computer usage via LSF, PBS or SGE queuing systems; source code is freely available under the GPL3 license at http://mocat.embl.de.Contact: bork@embl.deSupplementary information: Supplementary data are available at Bioinformatics online.

Thermodynamic Descriptions and Phase Diagrams for Pb-S and Bi-S Binary Systems

In this work, thermodynamic optimization of the Pb-S and Bi-S binary systems has been performed using the calculation of phase diagrams approach. The Gibbs free energies of the liquid phases in the two binary systems are treated with the associated solution model. The two intermediate compounds, i.e., PbS and Bi2S3, are modeled as stoichiometric phases. A set of self-consistent thermodynamic parameters for the Pb-S and Bi-S binary systems has been obtained by simultaneous optimization of the available thermodynamic and phase equilibria data, the results of which lead to good agreement between the calculated and experimentally measured data.

Chemical composition tuning in quaternary p-type Pb-chalcogenides – a promising strategy for enhanced thermoelectric performance

Recently a significant improvement in the thermoelectric performance of p-type ternary PbTe-PbSe and PbTe-PbS systems has been realized through alternating the electronic band structure and introducing nano-scale precipitates to bulk materials respectively. However, the quaternary system of PbTe-PbSe-PbS has received less attention. In the current work, we have excluded phase complexity by fabricating single phase sodium doped PbTe, alloyed with PbS up to its solubility limit which is extended to larger concentrations than in the ternary system of PbTe-PbS due to the presence of PbSe. We have presented a thermoelectric efficiency of approximately 1.6 which is superior to ternary PbTe-PbSe and PbTe-PbS at similar carrier concentrations and the binary PbTe, PbSe and PbS alloys. The quaternary system shows a larger Seebeck coefficient than the ternary PbTe-PbSe alloy, indicative of a wider band gap, valence band energy offset and heavier carriers effective mass. In addition, the existence of PbS in the alloy further reduces the lattice thermal conductivity originated from phonon scattering on solute atoms with high contrast atomic mass. Single phase quaternary PbTe-PbSe-PbS alloys are promising thermoelectric materials that provide high performance through adjusting the electronic band structure by regulating chemical composition.

Defects Are Needed for Fast Photo-Induced Electron Transfer from a Nanocrystal to a Molecule: Time-Domain Ab Initio Analysis

Quantum dot (QD) solar cells constitute an attractive alternative to traditional solar cells due to unique electronic and optical properties of QDs. In order to achieve high photon-to-electron conversion efficiency, rapid charge separation and slow charge recombination are required. We use nonadiabatic molecular dynamics combined with time-domain density functional theory to study electron transfer from a PbS QD to the rhodamine B (RhB) molecule and subsequent electron return from RhB to the QD. The time scale for the electron-hole recombination obtained for the system without defects agrees well with the experiment, while the simulated time scale for the charge separation is 10-fold longer than the experimental value. By performing an atomistic simulation with a sulfur vacancy, which is a common defect in PbS systems, we demonstrate that the defect accelerates the charge separation. This result is supported further by scaling arguments. Missing sulfur creates unsaturated chemical bonds on Pb atoms, which form the PbS conduction band. As a result, the QD lowest unoccupied molecular orbital (LUMO) is lowered in energy, and the LUMO density extends onto the adsorbed molecule, increasing the donor-acceptor interaction. The counterintuitive conclusion that defects are essential rather than detrimental to functioning of QD solar cells generates an unexpected view on the QD surface chemistry.

First Principles Study of Structural, Magnetic and Electronic Properties of PbX (X= S and Se) Doped with B, C and N

Six ternary compounds PbA0.75M0.25 (A=S and Se; M=B, C and N) with a NaCl structure were calculated to study the structure, electronic, and magnetic properties of them. The calculations were performed using the first-principles plane wave pseudopotential method within the generalized gradient approximation. The calculations reveal that ferromagnetism can be realized for C- and N-doping while B substitution does not induce magnetism in PbS and PbSe systems. The total energy calculations show that the ferromagnetic state is more stable as compared to a nonmagnetic state at their equilibrium lattices. Spin-dependent electronic band structure, total, and partial densities of state calculations demonstrate that the 2p-states of C- and N-dopants around Fermi level are responsible for ferromagnetism. Furthermore, equilibrium lattice constant, bond length, local magnetic moments, total magnetic moments, and robustness of ferromagnetism have been calculated. Particularly, the negative pressure calculations indicate that C-doping lead chalcogenides can change to half-metallic ferromagnetism materials.

Characterization of novel pneumatic mixing for single-use bioreactor application

Background The novel bioreactor system from PBS Biotech is the first with a pneumatic mixing device powered solely by gas buoyancy, eliminating the need for an external mechanical agitator. The patented design of the AirWheel mixing device promotes not only high tangential fluid flow around the wheel but also efficient radial and axial flows. The leverage effect of the Air-Wheel mixing device also allows for lower gassing requirement (v/v) with increasing working volume, making the power utilization from the gas buoyancy more efficient with scale. A series of physical tests were performed to demonstrate that PBS systems can promote uniform, homogenous mixing over a wide range of working volumes and can offer a low-shear environment for cell culture. A series of biological tests were then performed at various evaluation sites to confirm the physical test results.

Two Photon Emission and Nonlinear Optical Imaging of Acetonitrile-Treated Quasi-Spherical Nanoscale PbS Systems

The fabrication and nonlinear optical imaging of ~ 5-nm-sized lead sulfide (PbS) nanoscale particles prepared in a water-soluble polymer matrix is reported. The two photon excitation fluorescence (TPEF) studies (using Ti:Sapphire laser, λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ex</sub> ~ 706 nm, P = 400 mW, pulse ~ 80 fs) clearly show the foremost band-edge and asymmetric trap-related emissions. The chain-like organization of PbS nanoparticles was evident from the electron microscopy studies, and the impression from a cluster of nanopatterns was observable through laser scanning confocal microscopy. We have observed adequate correspondence between the TPEF spectra-based nonlinear optical images and spots corresponding to PbS nanoparticle assemblies. In addition, the PbS nanoparticles that are capable of producing strong second harmonic signals were efficiently imaged along the forward direction of the nonlinear microscopy. Investigation of two photon absorption processes along with the second-harmonic-generated imaging indicates the possibility of using the nanoscale particles in single molecule fluorescence spectroscopy, biomolecular labeling, and/or imaging applications.

Biodegradability of conducting chitosan- g-polycaprolactone/polypyrrole conduits

Conducting chitosan- g-polycaprolactone(CPC)/polypyrrole(PPy) conduits were fabricated for potential applications in nerve repair. Their mechanical and conducting properties as well as in vitro and in vivo degradation behaviors were mainly examined. It was found that some CPC/PPy conduits showed significantly stronger tensile and lateral compressive strength in the wet state, and notably higher conductivity in the overall tested PPy-load range, in comparison with chitosan/PPy conduits. After being consecutively exposed to PBS systems for various periods up to 10 weeks, the CPC/PPy conduits exhibited relatively slow degradation compared to chitosan/PPy conduits, and their degradation behaviors were measurably mediated by the composition of CPCs. The pH values of media corresponding to some selected CPC/PPy conduits did not significantly deviate from the initial pH value due to the buffering effect of chitosan component. After being implanted into rabbits for various periods, it was observed that the explanted chitosan/PPy conduits could only sustain a very low compressive load after 6-week degradation, and most of them were partially or fully collapsed after 8-week or longer degradation and showed very low conductivity. In contrast to these observations, some explanted CPC/PPy conduits were able to maintain enough strong mechanical strength in the wet state for the required period, and still showed acceptable conducting properties after 10-week in vivo degradation. Results suggested that some CPC/PPy conduits having proper compositional proportions could serve as desirable candidates to bridge nerve gaps in vivo.

Compressive mechanical properties and biodegradability of porous poly(caprolactone)/chitosan scaffolds

Porous polycaprolactone(PCL)/chitosan(CH) scaffolds with large pore sizes and high porosities were fabricated via a particle-leaching technique using hexafluoro-2-propanol as a shared solvent and salt (sodium chloride) particles as porogen. By optimizing processing conditions, numerous PCL/CH scaffolds with CH proportion lower than 50 wt% and similar pore parameters were built. These scaffolds were further evaluated for their compressive mechanical properties and biodegradation behaviors. It was found that their compressive modulus and stress at 10% strain were basically maintained in their dry state in contrast to their individual components, and these scaffolds still showed well-defined compressive characteristics and dimension stability even in their hydrated state compared with pure chitosan scaffolds. After being exposed to PBS or enzymatic degradation systems in vitro for various periods up to 10 weeks, it was observed that degradation of the PCL component could be accelerated at various rates depending on the compositions of the scaffolds and the media, and the chiosan component could effectively buffer the acidic degradation products of the PCL component.

Investigation of the Ln2S3—Cu2S—PbS (Ln: Y, Dy, Ho and Er) Systems.

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Investigation of the R 2S 3–Cu 2S–PbS (R = Y, Dy, Ho and Er) systems

The interactions between the components in the R 2S 3–Cu 2S–PbS (R = Y, Dy, Ho and Er) systems at 870 K were determined using X-ray single crystal and powder diffraction. The existence of the compounds RCuS 2 (R = Y, Dy, Ho and Er) and the solid solutions Y (2+ x)/3 Cu 2− x S 2 (0 ≤ x ≤ 0.52), Dy (2+ x)/3 Cu 2− x S 2 (0 ≤ x ≤ 0.55), Ho (2+ x)/3 Cu 2− x S 2 (0 ≤ x ≤ 0.61), Er (2+ x)/3 Cu 2− x S 2 (0 ≤ x ≤ 0.58) was confirmed in the R 2S 3–Cu 2S (R = Y, Dy, Ho and Er) sections. The existence of the compounds R 2PbS 4 (R = Y, Ho, Dy, Er) and the solid solution Dy 2+2 x/3 Pb 1− x S 4 ( x = 0.44–0.50) was established in the R 2S 3–PbS (R = Y, Dy, Ho and Er) sections. The formation of the compounds Y 5+ x Cu 1− x Pb 3− x S 11 ( x = 0.28), Dy 5CuPb 3S 11, Ho 5Cu 1+ x Pb 3− x/2 S 11 ( x = 0.25), Er 5CuPb 3S 11 in the R 2S 3–Cu 2S–PbS (R = Y, Dy, Ho and Er) systems was established at the first time, the existence of the compounds R 3.33CuPb 1.5S 7 (R = Y, Dy, Ho and Er) and RCuPbS 3 (R = Y, Dy, Ho and Er) was confirmed.

Optimization of contrast for MTN45 LCOS panel

— MTN45 LCOS was studied experimentally and by simulation. Optimized retardance and orientation of the compensation retarder were found by simulation and verified by experimental data for both wire-grid PBS and McNeil-type PBS systems. The parasitic reflectance from the counter-electrode (CE) glass and the retarder surface are two major effects that decrease the contrast of LCOS panels. Their effect was simulated by inserting several imaginary optical layers into the real system. Results also show that decreasing the retardance of the retarder; thus increasing the maximum driving voltage for the dark state can increase contrast. By combining all the improvements, we can achieve a contrast of 1500:1 in green and a contrast of 1000:1 in blue for MTN45 LCOS panels.

Phase Diagrams of the Quasi‐Binary Systems Cu2S—SiS2 and Cu2SiS3—PbS and the Crystal Structure of the New Quaternary Compound Cu2PbSiS4.

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Phase diagrams of the quasi-binary systems Cu 2S–SiS 2 and Cu 2SiS 3–PbS and the crystal structure of the new quaternary compound Cu 2PbSiS 4

X-ray phase analysis was used to investigated nine alloys with the general formula Cu 2PbB IVX 4 where B IV – Si, Ge, Sn; X – S, Se, Te. Only one compound of such composition was found, namely Cu 2PbSiS 4. Using differential thermal and X-ray phase analysis results, the phase diagrams of the Cu 2S–SiS 2 (in 0–60 mol% SiS 2 range) and Cu 2SiS 3–PbS systems were constructed. A congruent type of formation of Cu 8SiS 6 and Cu 2SiS 3 at 1459 and 1201 K, respectively, was confirmed in the Cu 2S–SiS 2 system. The Cu 2SiS 3–PbS system is quasi-binary with the formation of two quaternary intermediate phases, ∼Cu 4PbSi 2S 7 and Cu 2PbSiS 4. The ∼Cu 4PbSi 2S 7 compound forms incongruently at 1024 K, and has a polymorphous transition at 933 K. Cu 2PbSiS 4 melts in peritectically at 963 K and is also dimorphous. The phase transition temperature increases with PbS content in the 883–915 K range. The crystal structure of the low-temperature (LT) Cu 2PbSiS 4 modification was determined using powder method. It has trigonal symmetry (space group P3 221, a = 0.60565(2), c = 1.51841(5) nm, R I = 0.0641).

溶融ＦｅＳ‐ＰｂＳおよびＣｕ２Ｓ‐ＰｂＳ系の熱力学的研究

Vapour pressures of PbS in the pure PbS, FeS-PbS and Cu2S-PbS systems were measured by the transportation method within a temperature range from 1115 to 1170°C, and the activities of the components in the two binary systems were calculated. Also, the phase diagrams of the FeS-PbS and Cu2S-PbS systems were determined by the DTA method to compare with the experimental date of activities.The experimental results obtained are summarized as follows:(1) The vapour pressure of PbS in the range of 1115-117°C was given as: log PPbS/atm=-9193/T+5.69and the boiling point and heat of vaporization of PbS calculated from the equation of vapour pressure were 1341°C and 42. 0kcal/mol, respectively.(2) The activities of FeS and PbS in the FeS-PbS system at 1150°C exhibited nearly the ideal behavior, and the calculated activities from the phase diagram supposing a regular solution agreed with the experimental results.(3) The activities of Cu2S and PbS in the Cu2S-PbS system in the range of 1130-1170°C showed negative deviation from the Raoult's law, and they were little changed by differences in temperature. The activity coefficients at the infinite dilution of the components in the system were estimated 0.04 and 0.22 for Cu2S and PbS at 1150°C, respectivery.