Surface Morphology Transition Research Articles

Co‐encapsulation of ω‐3 LC‐PUFAs and carotenoids for enhanced synergistic antioxidant effects

AbstractThis work aimed to study the co‐encapsulation of ω‐3 Long‐Chain Polyunsaturated Fatty Acids (LC‐PUFAs) with β‐carotene, lutein and zeaxanthin and the cellular uptake of carotenoids. Monodisperse microcapsules with good properties, including particle surface morphology, water activity, microencapsulation efficiency, and glass transition temperature, were successfully prepared using a microfluidic‐jet spray drier with OSA‐modified starch as a wall matrix. The presence of carotenoids enhanced the oxidative stability of ω‐3 LC‐PUFAs. Caco‐2 cell uptakes of the carotenoids from the spray‐dried microcapsules were studied and compared to those encapsulated in the methylcellulose (MC) or xanthan gum (XG) delivery systems. The microcapsules encapsulated by OSA‐modified starch showed higher cellular uptakes of carotenoids (i.e., β‐carotene, 0.31 μg/mg protein; lutein, 0.52 μg/mg protein; zeaxanthin, 0.54 μg/mg protein) than those in the MC or XG delivery systems. The Caco‐2 cell uptake depended on carotenoid type, where hydrocarbon carotenoids (i.e., β‐carotene) had lower uptake than oxygenated carotenoids (i.e., lutein or zeaxanthin).

The electrical properties of nitrogen-doped vanadium dioxide thin films grown by magnetron sputtering

Abstract Vanadium dioxide (VO2) undergoes a reversible semiconductor-metal phase transition near 68°C, and the optical and electrical properties could be changed in femtoseconds. These unique characteristics meet the electro-optic switch applications. In this work, to improve the intrinsic characteristics of VO2, a series of nitrogen-doped vanadium dioxide thin films were prepared by reactive magnetron sputtering. Moreover, the effects of different nitrogen flow rates on the microstructure, surface morphology, electrical properties and phase transition properties of the samples were investigated. The samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), four-point probe system, and Hall effect et al. Sheet resistance variation at room temperature and high temperatures indicates remarkable semiconductor-metal transition characteristics. According to results of Hall effect measurement, when nitrogen flow rate is less than 1 sccm, the samples exhibits p-type semiconductor characteristics. However, while nitrogen flow rate reaches 1 sccm, n-type semiconductor characteristics appear. What’s more, Carrier mobility reaches a maximum at a nitrogen to oxygen flow ratio of 0.3. The results reveal that the samples have a great potential on electro-optic switching applications.

Improvement in organization of Cu–O coordination and super-electrons in Bi-2212 ceramic matrix with Ag/Sr partial substitution

This study rationalizes the reason for an increase in the electrical conductivity, crystal quality, surface morphology, and superconductive transition temperatures for Bi-2212 superconductors via scientific facts and discussions depending on replacing the optimum Ag/Sr sites in the system for the first time. Every experimental result and related calculations indicate the successful replacement of monovalent Ag+ ions for the divalent Sr2+ ions in the polycrystalline Bi-2212 structure. Moreover, it is observed that the bulk Bi-2212 ceramic prepared with a partial substitution level of x = 0.01 is observed to possess the highest electrical conductivity and superconductive transition temperatures of 84.68 K and 86.26 K for the Tcoffset\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{c}^{offset}$$\\end{document} and Tconset\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{c}^{onset}$$\\end{document}, respectively. Besides, in the case of the optimum replacement level, the Bi-2212 ceramic exhibits the most uniform and smoothest surface appearance, highest interactions between the grains, best microcrystal distributions/orientations, and largest average crystalline distribution along the crystal structure. In this regard, this study becomes a leader in broadening the application spectra including the heavy-industrial technologies, innovative, advanced engineering-related sectors, and large-scale application fields for Bi-2212 superconducting ceramics.

Synthesis and characterization of Co3O4 spinel nanowall: understanding the growth mechanism and properties

Formation of spinel tricobalt tetraoxide (Co3O4) nanostructures through a controlled thermal oxidation process is discussed here. Thin films of high purity cobalt (Co) were deposited on glass/quartz substrates using an electron beam (E-beam) evaporation technique. Thermal oxidation of the as-deposited Co thin films was carried out at various oxidation temperatures (400 °C to 600 °C) for different durations (5 h to 15 h) to grow various oxide nanostructures. Different surface characterizations techniques were used to investigate the structure, chemistry and electronic properties of the as-grown cobalt oxide nanostructures. x-ray diffraction analysis revealed the presence of the CoO phase along with the Co3O4 phases at relatively lower oxidation temperature. However, the Co3O4 phase becomes more predominant for longer oxidation durations at higher oxidation temperatures. Field emission scanning electron microscopy analysis showed a surface morphological transition from nanowalls to nanograins with an increase in the oxidation temperature. The surface electrical conductivity of the oxidized Co films is also increased for higher oxidation temperature and/or duration mainly due to the oxide phase purity and larger particle sizes. Ultraviolet–visible spectroscopy indicated two distinct optical energy bandgaps, which effectively decreased with an increase in the oxidation temperature and duration. Raman spectroscopy identified five different Raman-active modes corresponding to the Co3O4 phase, with the F2g mode dominating at higher temperatures. All these findings provide clear insights into the structural, electrical, chemical and optical properties of cobalt oxide thin films. Moreover, it provides a mechanism on how to grow 2D nanowalls morphology of Co3O4 films which can further be used in energy, sensor or catalytic applications.

Co-precipitation synthesis of highly pure and Mg-doped CdO nanoparticles: from rod to sphere shapes.

This study reports a facile approach for examining surface morphology transitions in semiconductor nanoparticles (NPs), with a focus on pristine and magnesium-doped cadmium oxide NPs. Mg-doped CdO NPs are synthesized via co-precipitation, and their composition, structure, and elemental distribution are analyzed through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectra, and X-ray photoelectron spectroscopy (XPS), along with optical characterization and impedance analysis. Doping with Mg2+ changes the morphology from rod-like to quasi-spherical, reduces the crystallite size, and impacts their structural and functional properties. Optical transmittance analysis revealed that Mg2+ doping resulted in a reduction of the band gap energy. Impedance spectroscopy demonstrates improved dielectric constant and electrical conductivity for Mg-doped CdO NPs. The Nyquist plots show grain effects and the equivalent circuit analysis corresponds to a R(CR)(CR) circuit. These advancements point to the potential of spherical Mg-doped CdO NPs in semiconductor applications due to their superior structural and functional characteristics.

Investigation on nano-grinding process of GaN using molecular dynamics simulation: Nano-grinding parameters effect

Nano-grinding is an essential step in ultra-precision machining for brittle material semiconductor workpieces in order to improve the surface quality and preserve strength prior to practical application. This study utilizes molecular dynamics (MD) method to conduct single-crystal gallium nitride (GaN) nano-grinding simulations under varying parameters. The damage mechanism of the surface/subsurface on the nanometer scale is explored through atomic displacement analysis, radial distribution function (RDF), phase transition, dislocation analysis, processing force, temperature distribution, and residual stress distribution. The machined surface quality and crystal structure distribution in the subsurface damage layer (SDL) are also examined, and a strong correlation is found between the parameters in nano-grinding. The nano-grinding speed is closely associated with the post-processing surface morphology, crystal phase transition, and temperature distribution in the GaN workpiece. Additionally, the ambient temperature has a considerable effect on the surface morphology and crystal phase transition. Moreover, the nano-grinding depth has a considerable influence on the surface morphology, phase transition, dislocation, processing force, and the temperature-dependent distribution of the residual stress in the GaN workpiece. This work reveals the relationship between the parameters and the mechanical properties of the machined surface in nano-grinding, and elucidates the damage mechanism of the subsurface, thus providing a helpful guide to the optimization of ultra-precision machining.

Investigation on surface morphology and phase transition characteristics in EDM for 8YSZ TBC on Inconel 718 superalloy

Investigation on surface morphology and phase transition characteristics in EDM for 8YSZ TBC on Inconel 718 superalloy

Metal–organic chemical vapor deposition of ε-Ga2O3 thin film using N2O as a precursor

The influence of N2O as a precursor is investigated for ε-Ga2O3 thin films grown under different conditions. The surface morphology and phase transition with the VI/III ratio were discussed based on the interplay of thermodynamic and kinetic effects.

Ordered stripes to crack patterns in dried particulates of DNA-coated gold colloids via modulating nanoparticle-substrate interactions.

The surface pattern in dried droplets of nanoparticle suspension possesses direct correlation with the evaporation profile, which apart from the bulk parameters, can also be altered by tuning the nanoscale interactions. Here, we show that, for sessile drops of DNA-coated gold nanoparticle (DNA-AuNP) solution, the alteration in evaporation pathway of TPCL (three-phase contact line) from stick-slip to mixed mode leads to a surface morphological transition from concentric rings with stripes to radial crack formation within the coffee ring deposit. A freshly cleaned silicon substrate offers hydrophilic/favorable substrate-nanoparticle interaction and produces multiple ordered stripes due to stick-slip motion of the TPCL. Using a SiO2/Si substrate with ∼200 nm of oxide layer leads to an increase in the initial water contact angle θi-w by ∼40°, due to increased hydrophobicity of the substrate. Three distinct modes of evaporation are observed - constant contact radius (CCR), constant contact angle (CCA) and mixed mode, resulting in the formation of radial cracks on a thick coffee ring structure. The critical thickness (hc), beyond which the cracks start to appear, was measured to be ∼600 nm and is in close agreement with the theoretical estimate of ∼510 nm. Through in situ contact angle and ex situ SEM measurements, we provide an understanding of the observed surface morphological transition in the dried particulate at various nanoparticle densities. Further analysis of the coffee ring width (d), linear crack density (σ) and crack spacing (λ) provides insight into the mechanism of crack formation for droplets dried on oxide-coated substrates.

Role of deposition temperature on non-linear optical properties of spray-coated Zn0.95Nd0.05O films

The influence of deposition temperature on the structure and optical (linear and nonlinear) properties of Zn0.95Nd0.05O thin films grown on glass substrates by using the spray pyrolysis method is studied. The X-ray diffraction spectra reveal the hexagonal wurtzite structure with a reduction in peak intensity as deposition temperature increases. With increasing temperature, the prominent peak intensity changes, and the dislocation density increases. Concomitantly, the surface morphology transitions from a nanoflake to a needle-like structure. With increasing deposition temperature, the optical transmittance of the films in the visible region improves, while the energy bandgap, refractive index and extinction coefficient values decrease. The reduction of refractive index and extinction coefficient values is ascribed to decreased scattering and uniformity of the films. Further, the films exhibit saturable absorption and films deposited at 300 ℃ show a maximum for third-order nonlinear susceptibility, which is quite appealing for nonlinear optical devices and components.

Synthesis and characterization of nanohydroxyapatite (nHAp) from Meretrix Meretrix Clam shells and its in-vitro studies for biomedical applications

Recycling of massive waste into valuable products promotes two in one advantages of waste recovery and a pollution-free environment. Preparation of Nanohydroxyapatite (nHAp) and its polymer composites using waste sea shells (natural precursor) are effectively useful in making artificial bone implants, bone cement, and toothpaste additives. The present work is focused to obtain nHAp with good crystalline nature and better biocompatibility using Meretrix Meretrix Clam shells as raw materials by the Co-precipitation method. To enhance the physio-chemical properties, polymers were used as capping agents. The functional group, particle size, thermal stability, phase transition, surface morphology, and electronic transition of atoms of the synthesized samples have been analyzed by spectrographic tools such as FT-IR, XRD, TG/DTA, FESEM/EDAX, XPS and HR-TEM with EDAX mapping respectively. Furthermore, the bacterial sensitivity of the sample against bacteria, the efficiency of the sample towards the formation of an apatite layer over the surface and its hemocompatibility nature were studied by antibacterial, SBF analysis and hemolysis assay respectively. This method of synthesis is free from hard chemicals and harmful by-products. Thus, the report of the present study suggests that it is promising to achieve nHAp with enhanced surface modification which indirectly promotes bone-bonding capability with natural living bone.

Influence of sapphire substrate miscut on the surface morphology and microstructure of AlN films grown by HVPE

The surface morphology and microstructure of c-plane AlN thick films grown by hydride vapor phase epitaxial (HVPE) have been firstly investigated in dependence on the miscut angle of sapphire substrates and the gas flow of HCl. AlN films grown on substrate with 0.2° miscut show relatively flat surface and the decreased HCl gas flow leads to the surface morphology transition from step-flow to step-bunching. Correspondingly, AlN thick films grown on substrate with 4° miscut at both HCl gas flow of 0.025 sccm and 0.015 sccm show step bunching morphology and the surface is rough. AlN thick films grown on sapphire substrate with 4° miscut have lower dislocation density, which is attributed to the macro-steps on the surface and the narrow atomic steps on substrates. Both macro-steps and narrow atomic steps promote the formation of inclined threading dislocations (TDs), thereby improving the quality of AlN thick films.

An Efficient Method to Transfer 2D Tmdcs Materials Via Novel Rapid Continuous Laser

The complex synthesis process and the limitations pertaining to substrates are the challenges that are encountered in the large-scale application of two-dimensional (2D) nanosheets. In the study, we developed an efficient method which can directly transfer low melting point 2D TMDCs materials at room temperature by 808-nm laser irradiation. This novel process can be used as a rapid universal technology to transfer predeposited low melting temperature materials, such as SnSex, NiSex and NbSex, on random substrates. By adjusting the laser power and irradiation time, we can design surface morphology, composition ratio and phase transition of transferred film. Besides, we have successfully transferred materials not only on common rigid single crystal Si or Al2O3 substrate but also on fragile materials such as paper and polyimide homogeneously without any damage. Furthermore, we demonstrated that transferred SnSex can be applied to electrode materials of energy storage system or sensing materials of photo-detector. This novel method paves the way for the scale-up synthesis of nanosheets on flexible substrates, which has enormous potential in photoelectronics and battery applications.

In Vitro Cell Interactions on PVDF Films: Effects of Surface Morphology and Polar Phase Transition.

In recent years, several studies have validated the use of piezoelectric materials for in situ biological stimulation, opening new interesting insights for bio-electric therapies. In this work, we investigate the morphological properties of polyvinylidene fluoride (PVDF) in the form of microstructured films after temperature-driven phase transition. The work aims to investigate the correlations between morphology at micrometric (i.e., spherulite size) and sub-micrometric (i.e., phase crystallinity) scale and in vitro cell response to validate their use as bio-functional interfaces for cellular studies. Morphological analyses (SEM, AFM) enabled evidence of the peculiar spherulite-like structure and the dependence of surface properties (i.e., intra-/interdomain roughness) upon process conditions (i.e., temperature). Meanwhile, chemical (i.e., FTIR) and thermal (i.e., DSC) analyses highlighted an influence of casting temperature and polymer solution on apolar to polar phases transition, thus affecting in vitro cell response. Accordingly, in vitro tests confirmed the relationship between micro/sub-microstructural properties and hMSC response in terms of adhesion and viability, thus suggesting a promising use of PVDF films to model, in perspective, in vitro functionalities of cells under electrical stimuli upon mechanical solicitation.

Controllable surface morphology transition from inter-connected pores to flower-like structures for super-hydrophobic poly (L-lactic acid) films

Abstract The Poly(L-lactic acid) (PLLA) films with polytropic surface morphology were fabricated by a modified solvent evaporation-induced precipitation method. In this novel method, the diffusion rate between solvent and non-solvent is mainly driven by the volatilization of the solvent and can be effectively controlled by covering the solvent with a non-solvent layer. In addition, inspired by the general Breath-Figure self-assembly, the controllable humidity is introduced to the system to adjust the solubility parameters of non-solvents, which avoids the instantaneous phase separation induced by direct coagulation of water droplets. The surface morphology realizes the transformation from inter-connected pores to flower-like structures by controlling polymer solution concentration and humidity. The surface water contact angle can reach to 152.1° with the combination of micro-scale flowers and nano-scale lamellar structures. Furthermore, the porosity of the prepared PLLA films can increase up to 87.5%, which greatly exceeds the 60% porosity of PLLA foam prepared by the non-solvent induced phase separation. Thus, the resultant film exhibits an excellent oil-absorption capacity even up to 17.88 g/g, which makes it has great application potential in the field of oil-water separation.

Lithium-antimony co-doping induced morphology transition in spray deposited SnO2 thin films

Un-doped, Sb doped (ATO) and Li-Sb co-doped SnO2 (LATO) transparent conducting thin film electrodes have been deposited using facile spray pyrolysis method. X-ray diffraction study is carried out to confirm the crystal structure, phase purity, and textured growth of the films. Surface morphological transition from dendritic to cuboid shape is observed upon Li-Sb co-doping into the SnO2 system from the scanning microscopy measurements. The AFM analysis confirms that as Li doping concentration (1, 3, 5 wt.%) increases, the surface roughness of the films decreases. The UV-Vis transmittance spectra of the SnO2 film doped with 5 wt.% Li and 5 wt.% Sb (LATO5) shows maximum average transmittance of 87.9 % at 550 nm and the calculated direct band gap value is 4.06 eV. The LATO5 film exhibits high carrier concentration and high mobility of 7.54 × 1020 cm−3 and 7.221 cm2/Vs, respectively, due to co-dopant effect at the Sn sites of SnO2 lattice, resulting in enhanced electrical transport properties compared to un-doped SnO2 film. The LATO5 film also exhibits lowest sheet resistance of 32.38 Ω/□ and resistivity of 1.57 × 10−3 Ω cm. The temperature dependent electrical conductivity study is performed to understand the conduction mechanism of the film via estimation of activation energy from Arrhenius plots. The obtained results indicate that the Li-Sb co-doped SnO2 films are potential candidates for alternative transparent conducting electrode system.

Tailoring Viruslike Mesoporous FeSe2 Hedgehogs for Controlled Drug Delivery and Synergistic Tumor Suppression.

To enhance affinity to their hosts, many organisms have evolved to be spiky. This strategy has been inspiring in many fields, but in drug delivery, the feasibility has not yet been extensively explored due to the lack of suitable nanocarriers. Herein, viruslike mesoporous FeSe2 hedgehogs with exceptional photothermal and catalytic performances have been tailored and explored for synergistic tumor therapy. The viruslike topology makes these hedgehogs highly prone to be internalized by cells. By uploading doxorubicin (Dox) into the hollow spikes and encapsulating the hedgehogs with photothermal-meltable gelatin, controlled surface morphology transition from quasi-spherical to spiky and accompanied Dox release have been achieved, with the assistance of the strong photothermal effect of FeSe2 hedgehogs. These integrated features allow specific and controlled drug delivery, leading to synergistic tumor suppression and immunogenic tumor cell death. These results provide new insights into the tailoring of drug carriers relying on their intrinsic physical features.

Tribological behaviour of atmospheric plasma and high velocity oxy-fuel sprayed WC-Cr3C2-Ni coatings at elevated temperatures

The thermally-sprayed coatings extensively used in high temperatures application such as aerospace, power generation equipment, hot section components in gas and steam turbines. Most of the thermally sprayed WC based coatings lost the functional ability after 500 °C. Consequently, the work focuses on the development of WC based coatings which could sustain with excellent functional ability even above 500 °C. The unidirectional dry sliding wear of WC-Cr3C2-Ni coatings deposited by atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) techniques have been relatively investigated up to 800 °C using ball-on-disc high-temperature tribometer (ASTM G99). The scanning electron microscopy (SEM), energy dispersive X-ray analyser (EDX) and Raman spectroscopy analysed the worn-out surface morphology, oxide content and phase transition. The detailed wear mechanisms at 300 °C, 500 °C and 700 °C were studied. Interestingly, the specific wear rates of both the coatings were declined after 500 °C. The study of the relationship between wear and tribo-oxidation process suggested that HVOF coatings inhibit the wear above 500 °C, due to development of tribo-film and well retained WC phase on the surface even at high temperature. The lubricous oxides WO3, NiWO4 and CrWO4, attributed to form a tribo-oxide film which resulted into superior wear resistance up to 800 °C. Nevertheless, specific wear rates for both coatings are in a mild regime which recommended that WC-Cr3C2-Ni coatings could be more durable up to 800 °C in the oxygen-enriched environments.

In Situ Raman Microscopy for Redox Mechanism of Cathode Materials

Raman spectroscopy has been used to study structural information is a vibrational technique which is very sensitive to the metallic oxidation state, and it is very suitable for electrode materials due to several characteristics; fast, nondestructive method, measurement of the same electrode and even on the same spot with various laser, and analysis using another techniques. Moreover, the Raman imaging technique is powerful tool to study the charge of structure, surface morphology, and phase transition accompanying crack propagation. Here, we introduce Raman micro-spectroscopy installed at Advanced Nano-Surface Research Group in KBSI which is especially set up in glove box to measure various materials without air exposure, which can exhibit a sample from another surface contamination when exposure to atmosphere. Additionally, we designed and fabricated two types of electrochemical cells (plane cell and cross cell) developed for in situ Raman micro-spectroscopy for studying electrode materials in operating battery during battery operation. This approach simultaneously characterizes phase transition and facilitates uncovering the relationships between surface structure and activity during battery operation. This result provides a method for visualizing chemical structure of phase transition and the changed surface morphology.

Corrosion resistance with self-healing behavior and biocompatibility of Ce incorporated niobium oxide coated 316L SS for orthopedic applications

Ceramic oxide coatings are widely used in biomedical applications due to their ability to bond with bone and soft tissues. In the present study, we focus on improving the biocompatibility and corrosion resistance with self-healing properties of 316L SS by coating with cerium (Ce) incorporated niobium oxide (Nb2O5) bioceramics synthesized by sol-gel technique. The effect of Ce concentrations in Nb2O5 on the surface properties of 316L SS and its self-healing process during electrochemical corrosion in simulated body fluid (SBF) were deeply analyzed. The surface functional groups, morphology, chemical composition and phase transitions present in the coatings were analyzed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), high resolution scanning electron microscopy (HRSEM) with elemental dispersive X-ray (EDX) and X-ray diffraction (XRD) studies respectively. Chemical states of Ce and Nb in the Ce incorporated niobium oxide coating were identified by X-ray photoelectron spectroscopic (XPS) studies. Results show that Ce is present as both Ce3+ and Ce4+ oxidation states in CeO2 form whereas Ce3+ is the main species and Nb is present as Nb5+ oxidation state exists in Nb2O5 form. Ce incorporated Nb2O5 coatings improved the surface roughness (Ra) and hydrophilic nature of 316L SS, studied through atomic force microscopy (AFM) and water contact angle measurements. Electrochemical studies were performed for the specimens immediate and after 7 days immersions in SBF solution to evaluate the corrosion resistance with self-healing behavior. Results show that increased corrosion resistance with reduction in current density (icorr) and corrosion potential (Ecorr) and breakdown potential (Ebreak) shifts towards more positive potentials from potentiodynamic polarization studies whereas increased impedance values and good capacitance behavior in the low frequency regions were measured from electrochemical impedance spectroscopic (EIS) studies for the Ce incorporated Nb2O5 coated 316L SS specimens. Cell culture studies were performed on specimens using osteoblast MG 63 cells, among those Ce incorporated Nb2O5 coatings were showed enhanced biocompatibility for 316L SS with improved cell adhesion, significant cell spreading, proliferation and differentiation of cells.