Evaporation Procedure Research Articles

High current density photocathode for CW terahertz photoconductive vacuum devices

For vacuum electronics-related terahertz (THz) sources, robust, quick-response, and tunable continuous emission electron emitters are still challenging. In this paper, a continuous emission high current density Na2KSb(Cs) photocathode is developed and verified experimentally. The photocathode emission enhancement is achieved through optimization of film thickness, adjustment of the cesium activation, and dynamic optimization of the quantum efficiency during the synthesis process. The detailed evaporation procedures to perform the photocathode growth is investigated and reported. To maintain a higher current density, performances of photocathode evaporated on borosilicate glass and sapphire are tested respectively and analyzed comparatively. The results show that remarkable continuous current density can be achieved at 30 mA/cm2 on glass substrates, and 3 A/cm2 on sapphire substrates respectively. We found that the thermal conductivity of the substrates has a significant impact on high current density operations. The optimal emission current density has reached a promising value for future excitation of continuous wave (CW) THz wave radiation based on the photoconductive vacuum devices. These results also offer an opportunity to approach the generation and temporal shaping of planar array electron beams for THz vacuum tubes.

Improved sample preparation procedure for gross alpha counting on gas-flow proportional counter

Sample residue uniformity is crucial for accurate gross alpha counting using a gas-flow proportional counter, however this can be difficult to achieve using conventional procedures. An evaporation method using a 1:1 mixture of deionized water and 2-propanol yielded uniform 230Th and 241Am nitrate salt residues on metal planchets for gross alpha counting. The gross alpha efficiency and alpha:beta crosstalk behavior were studied using the evaporation procedure and a separate barium sulfate/ferric hydroxide coprecipitation method. The gross alpha efficiency data were fitted with empirical power law functions. The alpha:beta crosstalk behavior was different for the two radionuclides studied.

A new sample treatment strategy based on simultaneous supramolecular solvent and dispersive solid-phase extraction for the determination of ionophore coccidiostats in all legislated foodstuffs

A single-step sample treatment, for the simultaneous extraction and clean-up for the determination of ionophore coccidiostats in EU legislated foodstuffs, is here proposed. The treatment is based on the combination of: (i) a supramolecular solvent with restricted access properties (SUPRAS-RAM), spontaneously formed by the addition of hexanol, water and THF to the sample; and (ii) dispersive solid phase extraction (dSPE). The SUPRAS-RAM extract was directly compatible with LC-MS/MS and no further re-extraction, evaporation or cleanup procedures were necessary. SUPRAS-RAM efficiently extracted the ionophores (recoveries in milk, eggs, fat, liver, kidney, and chicken and beef muscle were in the range 71–112%) and removed proteins and carbohydrates, whereas dSPE removed fats and other lipophilic compounds. The method was validated following the European Commission Decision 2002/657/EC. Detection limits (0.004–0.07 µg kg−1) were far below the maximum residue limits (1–150 µg kg−1). Method analytical and operational characteristics were suitable for routine determination of ionophores.

Features of Au(80)Sn(20) thin film solder manufacturing technology

This work provides the results of manufacturing technology development for Au(80)Sn(20) thin film solders produced with electron-beam evaporation coating of alternating gold and tin layers. The phase formation mechanism in the produced solders was studied to work out an evaporation procedure which enables to make a solder with the properties meeting the requirements to soldering of a laser diode onto a heatsink base surface.

Elimination of residual solvent from PLGA microspheres containing risperidone using supercritical carbon dioxide

This investigation aimed to eliminate the residual organic solvent dichloromethane (DCM) from microspheres containing risperidone using supercritical carbon dioxide (scCO2). A conventional emulsion-solvent evaporation procedure was used to prepare the microspheres, and scCO2 eliminated the residual DCM. To obtain the maximum elimination yield %, central composite design (CCD) with the parameters of static time, dynamic time, pressure, and temperature was applied. After scCO2 treatment, the residual DCM was analyzed using headspace GC-FID. Finally, the characterization, encapsulation efficiency, drug loading, and in-vitro release of the microspheres were also investigated. For maximum elimination % of residual DCM using scCO2 (99.43%), the static time, dynamic time, pressure, and temperature were 21.31 min, 119.17 min, 226.44 bar, and 44.77 °C, respectively. DCM contents of the risperidone-PLGA microspheres before and after scCO2 treatment were 4612 ± 198 μg/mL and <21.93 μg/mL, respectively. The mean particle sizes, pore diameter, and porosity after scCO2 treatment were higher than the pre-treatment values. ScCO2 technology could increase both porosity and DCM removal, which enhances the uniform distribution of the drug in the matrix. The microspheres before scCO2 treatment contains larger amounts of solvents, which could enhance polymeric chain mobility and thus drug release. Consequently, it leads to the sustained release of the drug from the microsphere matrix.

Coordination-Induced Self-Assembly of a Heteroleptic Paddlewheel-Type Dirhodium Complex

A novel heteroleptic paddlewheel-type dirhodium (Rh2) complex [Rh2(O2CCH3)3(PABC)] (1; PABC = para-aminobenzenecarboxylate), which has an amino group as a potential donor site for coordination with the metal ion, was synthesized and characterized by 1H NMR, ESI-TOF-MS, infrared spectra, and elemental analysis. The slow evaporation of N,N-dimethylformamide (DMF)-dissolved 1 produces the purple-colored crystalline polymeric species [Rh2(O2CCH3)3 (PABC)(DMF)]n (1P). Single-crystal and powder X-ray diffraction analyses, as well as thermo-gravimetric analysis, clarified that 1P formed a one-dimensional polymeric structure, in which the two axial sites of the Rh2 ion in 1P are coordinated by a DMF molecule and an amino group of the PABC ligand of the neighboring molecule 1, by coordination-induced self-assembly (polymerization) with an Rh-amino bond. The reversible structural change (self-assembly and disassembly transformations) between the discrete species [Rh2(O2CCH3)3(PABC)(DMF)2] (1D; green solution) and the polymeric species 1P (purple solid) was accompanied by a color change, which easily occurred by the dissolution and evaporation procedures with DMF.

High Seebeck coefficient in thermally evaporated Sb-In co-alloyed bismuth telluride thin film

In the present work, we have obtained high magnitudes of the Seebeck coefficient in Sb and In coalloyed bismuth telluride thin film that has been deposited by a simple and cost-efficient thermal evaporation procedure. The films display an exceptional peak Seebeck coefficient of −310 μV/K at the working temperature of 90 °C. In addition to this, a high value of −191.6 μV/K is obtained at room temperature along with appreciable conductivity (6.2 × 103 S/m). The x-ray diffraction (XRD) pattern of the film has been analyzed for probing the crystal profile that depicts a polycrystalline and nanoscale structure. Films’ surface and cross-sectional morphologies are investigated using Field Emission Scanning Electron Microscope (FESEM), where a nanocrystalline morphology of thickness 150 nm is observed. Raman analysis supports the results obtained from XRD and FESEM for nanomorphology and indicates the presence of Te segregates. Atomic composition of the film produced is probed using Energy Dispersive x-ray spectroscopy, which also indicates the presence of excess Te. The Seebeck coefficient of the films shows an enormous enhancement as compared to previously reported work for undoped samples (BST-100S). The magnitudes of the Seebeck coefficient obtained in the present work are among the highest values reported for a bismuth antimony telluride material. These enhancements are attributed to the combined effect of coalloying, the presence of highly mobile (00l) orientations, and confinement effects of a nanocrystalline profile.

Structural, optoelectrical, linear, and nonlinear optical characterizations of the Cu2ZnGeSe4 thin films

Good quality copper zinc germanium selenide (Cu2ZnGeSe4) thin films were grown via thermal evaporation procedure with different thicknesses (261, 379, and 486 nm). The analysis of the X-ray diffraction examination of the Cu2ZnGeSe4 thin films demonstrates that the as-deposited Cu2ZnGeSe4 thin films are polycrystalline with a single-phase tetragonal structure. The elemental composition analysis of the evaporated Cu2ZnGeSe4 thin film established that the as-deposited film is near stoichiometric in the compound. The optical study on the Cu2ZnGeSe4 thin films displayed that the Cu2ZnGeSe4 films exhibited a direct allowed optical transition and by increasing the thickness the magnitudes of the direct bandgap were decreased from 1.47 to 1.31 eV while the Urbach energy increased. The effect of thickness on the skin depth δ, absorption coefficient , linear refractive index n, and the static refractive index no of the Cu2ZnGeSe4 thin films was studied. The analysis of the nonlinear optical parameters of the Cu2ZnGeSe4 thin films reveals the increase of the film thickness combined with increase in the nonlinear refractive index.

Structural, optical, optoelectrical and photovoltaic properties of the thermally evaporated Sb2Se3 thin films

Production of inexpensive and promising light-absorbing materials is very important in photovoltaic device applications. In this study, we investigate the preparation of good-quality antimony selenide (Sb2Se3) thin films via thermal evaporation procedure with different thicknesses (241, 315, 387 and 429 nm). The analysis of the X-ray diffraction examination of the Sb2Se3 thin films demonstrates that the as-deposited Sb2Se3 thin films are polycrystalline with a single-phase orthorhombic structure. The elemental composition analysis of the evaporated Sb2Se3 thin film established that the as-deposited film has near stoichiometric composition of the compound. The linear optical results of the Sb2Se3 thin films revealed that the films show optical direct transitions and optical energy gaps in the range 1.12–1.05. The optoelectrical parameters of the Sb2Se3 thin films (ratio of the charge carrier concentrations to the effective mass $$N_{\text{opt}} m$$, optical electronegativity $$\xi_{\text{opt}}$$ and the lattice dielectric constant, $$\varepsilon_{L}$$) were estimated. The analysis of nonlinear optical parameters of the Sb2Se3 thin films reveals the increase of the film thickness combined with increase in the nonlinear refractive index. The Al/n-Si/Sb2Se3/Ag heterojunction was produced by the thermal evaporation technique. The photovoltaic constants of the Al/n-Si/Sb2Se3/Ag heterojunction were estimated from the J–V curve and demonstrate a solar efficiency of 4.03%.

From hollow lignin microsphere preparation to simultaneous preparation of urea encapsulation for controlled release using industrial kraft lignin via slow and exhaustive acetone-water evaporation

AbstractLignin nano/microparticles have recently attracted growing interest for various value-additive applications of lignin, especially encapsulation. In this study, in order to establish a highly efficient and highly productive preparation process to effectively utilize technical lignin, a brand-new, slow and exhaustive solution evaporation process following a simple, self-assembly principle was developed using industrial softwood kraft lignin (SKL) from a starting acetone-water (80/20, v/v) solution to recover 100% of the lignin as homogeneous and well-shaped microspheres. The prepared microspheres had a typical average diameter of 0.81 ± 0.15 μm and were hollow with very thin shells (of nanoscale thickness). Based on this developed technique, encapsulation of urea by these lignin microspheres was directly achieved using the same process as hollow lignin microspheres with urea attached to the outside and entrapped inside of the wall. Two distinct urea release rates were observed for the urea-encapsulated microspheres: a fast release of the urea outside the shell wall and a slow (controlled) release of the urea inside the shell wall. The encapsulation efficiency was as high as 46% of the trapped urea as encapsulated inside the lignin microspheres. The slow and exhaustive solution evaporation procedure reported here is a simple and straightforward method for the valorization of industrial kraft lignin as hollow microspheres with controllable, homogeneous and desired morphologies, and especially for the direct preparation of lignin-based encapsulating fertilizers for controlled release.

Hybrid perovskite charge generation layer for highly efficient tandem organic light-emitting diodes

Abstract Perovskite films are an emerging class of semiconductors with considerable potential for using inactive layer that has been extensively studied in solar cells and light emitting diode fields. In this work, we propose a new application of perovskite materials as a charge generation layer (CGL) in the field of optoelectronic devices. Here, perovskite material CsPbBr3 and n-type material fullerene carbon 60 (C60) are accurately controlled by a crystal oscillator in the vacuum thermal evaporation chamber. The prepared perovskite material possesses the properties required as an ideal charge generation layer material, making it suitable as a CGL. The efficiency of tandem organic light emitting diode with the C60/CsPbBr3 CGL is significantly improved, a value of 31.2 cd/A, which is 2.1 times higher than that of the single-emitter device. This achievement stems from the proposed thermal evaporation procedure avoids some side effects caused by dopants in traditional CGL, simultaneously provides high luminescence and balanced charge injection.

Selective crystallization of gamma glycine for NLO applications using magnesium sulfate (MgSO4) as an additive

Abstract Crystallization of γ-glycine in the presence of selected concentration (9 g/mL) of tailor-made additive magnesium sulfate heptahydrate salt (MgSO4·7H2O) has been studied at ambient temperature by adopting slow solvent evaporation procedure. The morphological modifications of glycine crystals grown from pure aqueous solutions of glycine and from glycine solutions containing magnesium species in the amount of 0.1 g/mL to 16 g/mL have been investigated thoroughly. The crystalline nature and phase identification of the crystalline material were confirmed by X-ray powder diffraction and SXRD studies. NMR studies revealed the information about the molecular conformation in solution, phase changes, functional groups and chemical environment. FT-IR spectra revealed distinct difference between α and γ-glycine polymorphs in the region around 880 cm−1 to 930 cm−1. The grown γ-glycine crystal had a lower cut-off value at 200 nm and the bandgap value evaluated from the Tauc plot was found to be 5.83 eV. The marked differences between α and γ-polymorphs of glycine were also revealed by DSC thermograms. The mechanical strength of the γ-glycine crystal was studied with the help of Vickers microhardness instrument. Kurtz-powder NLO study proved the generation of second harmonics (i.e. green light emission) in the grown γ-glycine crystal and its efficiency was calculated as 1.44 times better than that of the reference material potassium dihydrogen phosphate.

Structural, optical and dielectric properties of n-type organic N,N′-dimethyl-3,4,9,10-perylenedicarboximide thin films: effects of annealing

N-type N,N′-Dimethyl-3,4,9,10-perylenedicarboximide ((PTCDI-C1) organic thin films were fabricated by vacuum evaporation procedure. The crystallinity of PTCDI-C1 was analyzed by x-ray diffraction(XRD), while its structure was studied by scan electron microscopy (SEM). The optical properties of as-prepared and annealed PTCDI-C1 thin films were determined by double beam spectrophotometer. The results of XRD and SEM revealed the increase of agglomeration grain size due to thermal effect. The transmittance and reflectance were measured in visible and ultraviolet wavelength spectrum. The normal dispersion of refractive index was modeled according to single oscillator model. For higher energy range (hv > 3.5 eV), the calculated optical conductivity of PTCDI-C1 thin films was observed to increase with increasing of the photon energy. The optical band gap energy of the annealed PTCDI-C1 thin films was found to be decreased as a direct effect of temperature increase. Furthermore, the value of the third nonlinear susceptibility χ(3) values of thin film were lowered as a result of annealing.

Phosphonylation Controls the Protein Corona of Multifunctional Polyglycerol-Modified Nanocarriers.

Nanocarriers are a platform for modern drug delivery. In contact with blood, proteins adsorb to nanocarriers, altering their behavior in vivo. To reduce unspecific protein adsorption and unspecific cellular uptake, nanocarriers are modified with hydrophilic polymers like poly(ethylene glycol) (PEG). However, with PEG the attachment of further functional structures such as targeting units is limited. A method to introduce multifunctionality via polyglycerol (PG) while maintaining the hydrophilicity of PEG is introduced. Different amounts of negatively charged phosphonate groups (up to 29 mol%) are attached to the multifunctional PGs (Mn 2-4 kg mol-1 , Ð < 1.36) by post-modification. PGs are used in the miniemulsion/solvent evaporation procedure to prepare model nanocarriers. Their behavior in human blood plasma is investigated to determine the influence of the negative charges on the protein adsorption. The protein corona of PGylated nanocarriers is similar to PEGylated analogs (on same nanocarriers), but the protein pattern could be gradually altered by the integration of phosphonates. This is the first report on the gradual increase of negative charges on nanocarriers and intriguingly up to a certain amount of phosphonate groups per nanocarrier the protein pattern remains relatively unchanged, which is important for the future design of nanocarriers.

Molecular Power Spring: Circular Dichroism Inversion of Polythiophene Aggregates from the Right-Handed Helix to Left-Handed Helix.

In molecular rotors, a type of molecular machine, spontaneous rotors without the need for an external stimulus are promising because conventional molecular rotors require a continuous energy supply. In this study, we demonstrate spontaneous transformation from kinetically favored metastable right-handed helical aggregates to thermodynamically stable left-handed helical aggregates after an evaporation procedure. In addition, we propose the conditions for preparation of metastable right-handed helical aggregates, whose chirality can be spontaneously inverted, based on kinetic analysis. This molecular power spring will be useful for designing new types of molecular machines.

Calibration of 2‐D soil zymography for correct analysis of enzyme distribution

Soil zymography is a new technique developed to visualize two‐dimensional distributions of enzyme activities. The method consists of incubating a membrane saturated with an enzyme‐specific fluorogenic substrate on a surface of the soil sample, followed by recording the membrane image generated by a fluorescent product (e.g. MUF: methylumbelliferone) in ultraviolet light. Despite its relative ease of use, performing zymography involves multiple user‐made decisions that might affect the accuracy of enzyme activity estimates. Therefore, unification of the zymography methodology is required for correct estimations and comparisons of various studies. We evaluated the following methodological aspects of the implementation of zymography: (a) camera settings and image processing, (b) effects of evaporation and (c) calibration procedures. Camera settings (shutter speeds or exposure time) affected the intensity of background fluorescence and signal‐to‐noise ratios (SNR). However, because their combined effects varied depending on MUF concentrations, light and camera setting need to be optimized for the expected range of MUF concentrations prior to zymography. Evaporation of MUF solution from the membrane had no effect on fluorescence. Relations between MUF concentration and intensity of fluorescence during calibrations demonstrated a saturated pattern and were strongly affected by image noise outside the optimal range (e.g. 8–14 μm MUF pixel−1). We developed a new calibration approach that is based on a piecewise linear regression. The new approach accounted for specific ranges of MUF concentration and uses nonuniformly saturated membranes, reflecting the real distribution of enzyme activities in soil. The new calibration algorithm eliminated biases of the standard calibration and resulted in greater accuracy in predicting MUF concentrations.Highlights We developed a new approach to calibration for 2‐D soil zymography. The approach accounted for spatial nonuniformity of soil zymograms. Standard calibration resulted in systematic underestimation of enzyme activity. Soil zymography requires pixel‐based calibration with nonuniformly saturated membranes.

Characterization on crystal structure of CH3NH3PbIxCl3−x perovskite by variable temperature powder X-ray diffraction

In this work the CH3NH3PbIxCl3−x perovskite is obtained by applying vacuum-rotary evaporation procedure with a precursor solution of PbCl2 and CH3NH3I in dimethylformamide. Thermal gravimetric and differential thermal analysis (TG-DTA) and the variable temperature powder X-ray diffraction (in situ XRD) are employed to research the effect of thermal treatment on the decomposition and the crystal structure of perovskite. It is found that tetragonal to cubic phase transition in the typical perovskite disappears in mixed perovskite crystals because the stabilizing action of Cl. The excess Cl in the precursor leads to the intermediate structure CH3NH3PbCl3, and then transforms into CH3NH3PbI3 with temperature increasing.

On-line solvent exchange system: Automation from extraction to analysis

Removal of organic solvent from sample extracts is required before analysis by reversed phase HPLC to preserve chromatographic performance and allow for bigger injection volumes, boosting sensitivity. Herein, an automated on-line extraction evaporation procedure is integrated with HPLC analysis. The evaporation occurs inside a 200 μm microfluidic channel confined by a vapor permeable membrane. A feedback control algorithm regulates evaporation rate keeping the output flow rate constant. The evaporation process across this membrane was firstly characterized with water/solvent mixtures showing organic solvent removal capabilities. This system allowed continuous methanol, ethanol and acetonitrile removal from samples containing up to 80% organic solvent. An evaporative injection procedure was developed demonstrating the use of the device for fully integrated extract reconstitution coupled to HPLC analysis, applied to analysis of the antibiotic chloramphenicol in milk samples. Sample reconstitution and collection was performed in less than 10 min and can be executed simultaneously to HPLC analysis of the previous sample in a routine workflow, thus having minimal impact on the total sample analysis time when run in a sequence.

Paclitaxel‐Loaded PLA/PEG/Magnetite Anticancer and Hyperthermic Agent Prepared From Materials Obtained by the Ugi's Multicomponent Reaction

In this study, Magnetic microspheres formed by Magnetite, Paclitaxel (PCT), poly(lactic acid) (PLA), and poly(ethylene glycol) (PEG) diblock copolymers material, synthesized by the Ugi four‐component condensation reaction (UFCC), are prepared by single emulsion and solvent evaporation procedure. Prepared PCT‐loaded magnetic microspheres (PCTMMS) are characterized by magnetic induction hyperthermia (MIH), SEM, and LDS techniques. Microencapsulation process yielded PCT encapsulation efficiency (Ee) between 70 and 80%, determined by HPLC analysis of the resulting supernatant after the microencapsulation process. A kinetic study of drug release in vitro using HPLC showed a sustained and controlled release of PCT. Also, the presence of an external magnetic field speeds up the kinetic release profile of PCT. Anticancer activity of release medium against intestine cancer cell line (Caco2) is determined using the cell viability assay. PCTMMSs are able to inhibit cancer cell growth and colony formation. The main contribution of these results is to propose a new application for UFCC in the preparation of one anticancer and hyperthermic drug delivery systems (DDS) able to improve the cancer treatment and even the welfare of the patients.

Experimental comparison and optimization guidance of R1233zd(E) as a drop-in replacement to R245fa for organic Rankine cycle application

The organic Rankine cycle is capable of converting the low-temperature waste heat into electricity. The commonly used working fluid R245fa will be phased out in the near future because of the significant impact to climate change. In that case, a new refrigerant R1233zd(E) with extremely low GWP is proposed as an environmental friendly substitute in this paper. The investigation is processed with four steps: firstly, a thermodynamic analysis was carried out for prior prediction of the applicability of R1233zd(E) as an alternative to R245fa; secondly, an experimental comparison between two refrigerants was implemented under a design of extensive operating conditions; Afterwards, experimental results were presented. Differences in expansion and evaporation procedure based on three non-dimensionless indicators were analyzed; Eventually, a multi-objective optimization guidance involved with aforementioned indicators was proposed. Comparing the maximum cycle thermal efficiency, R1233zd(E) leads to approximately 3.8% higher than R245fa. Comparing the maximum output electrical power, R1233zd(E) leads to 4.5% better than R245fa. R1233zd(E) is proven as an appropriate alternative to R245fa based on current study. Prediction precision of the volume ratio dependent curves of filling factor and isentropic effectiveness are within 1.2% and 2.7%, which can be used to model a certain expander in optimization procedure.