Field Emission Scanning Electron Micrographs Research Articles

PVC/CNT Electrospun Composites: Morphology and Thermal and Impedance Behavior.

Due to their mechanical robustness and chemical resistance, composite electrospun membranes based on polyvinyl chloride (PVC) are suitable for sensor applications. Aiming to improve the electrical characteristics of these membranes, this work investigated the effects of the addition of carbon nanotubes (CNTs) to PVC electrospun membranes, in terms of morphology and thermal and impedance behavior. Transmission electron microscopy images evidenced that most of the nanotubes were encapsulated within the fibers and oriented along them, while field-emission scanning electron micrographs revealed that the membranes consisted of uniform fibers with an average diameter of 339 ± 31 nm, regardless of the addition of the carbon nanotubes. With respect to the neat resin, the addition of nanotubes caused a significant lowering of the glass transition temperature (up to 20 °C) and a marked change in the second degradation step of PVC. Nyquist plots from electrical impedance spectra showed a charge transfer resistance (RCT) of 38 and 40 MΩ for neat PVC and PVC/CNT 3 wt.% membranes, respectively, indicating that, in the dry state, the encapsulation of CNTs in the fibers and the high porosity of the membranes prevented the formation of a percolation network, increasing the electrical resistance. In the wet state, however, there was a greater change in the impedance behavior, decreasing the resistance RCT to 4.5 and 1.1 MΩ, for neat PVC and PVC/CNT 3 wt.% membranes, respectively. The results of this study, showing a significant variation in impedance behavior between dry and wet membranes, are relevant for the development of various types of sensors based on PVC composites.

Structural and Optical Properties of Magnetron-Sputtered Chromium Oxynitride Thin Films

Doping non-metal elements into Cr2O3 can tailor its properties, making it more efficient for applications like sensors or photocatalysis. For this purpose, the current research work presents the impact of nitrogen doping on the structural and optical properties of Cr2O3 thin films. Pure and N-doped Cr2O3 (Cr2O3−xNx) thin films were synthesized using the DC reactive magnetron sputtering approach. The stoichiometry was obtained by raising values of x, where x = 0, 0.125, 0.25, and 0.50. X-ray diffraction analysis confirmed the rhombohedral crystal structure without the presence of any other secondary phase in undoped and N-doped Cr2O3 thin films. Furthermore, crystallinity and average crystallite size have enhanced by doping. Field emission scanning electron micrographs disclosed that the surface morphology of the prepared samples changed considerably with doping. A thorough optical investigation was carried out by spectroscopic ellipsometry. Several optical properties significantly changed with dopant content. The reduction in the optical bandgap from 2.50 eV to 1.82 eV, with N-doping was observed. The study demonstrated that N-doping improves the structural and optical properties that make it a promising candidate for optoelectronic applications.

Kinetics of crystallization and soft magnetic properties of Co72Fe8B10Si10 amorphous alloys

Co72Fe8B10Si10 amorphous alloy was prepared in an Ar atmosphere using a single roller rapid quenching technique at a wheel speed of 25 m/s. The prepared ribbons were annealed for 1 h at temperatures ranging from 473 to 773 K. X-ray diffractometer was used to observe the microstructure transformation. Field emission scanning electron micrographs exhibit mosaic type structures that become more prominent with increasing annealing temperature. Energy dispersive X-ray spectroscopy was also utilized to observe the concentrations of elements. The Kissinger and Ozawa equations were utilized to determine the amorphous alloy's crystallization activation energy. The two methods revealed consistent findings in their calculations. At 473 K, the obtained maximum real initial permeability (μ′max) is 376 which remains unchanged up to 10 kHz, whereas for 573 K, μ′max is noted to be 361 to 100 kHz. Other magnetic parameters such as loss factor, quality factor, and relative quality factor were also investigated for the Co72Fe8B10Si10 amorphous alloy to elucidate its suitability in such materials based devices.

Optical characterization and dispersion analyses of plasma polymerized methyl acrylate thin films

This work reports the structural characteristics, surface morphology, linear and nonlinear optical properties of 110 to 225 nm thick plasma polymerized methyl acrylate (PPMA) thin films. X-ray diffraction analyses confirm the amorphous nature of the films. Field emission scanning electron micrographs of the films display cluster-based surface morphology. Attenuated total reflectance Fourier transform infrared spectroscopy confirms the chemical structural changes in the films. The optical properties were studied based on the absorbance, transmittance, and reflectance spectra measured by an ultraviolet–visible spectrophotometer within the wavelength ranges from 200 to 800 nm. The direct optical band gap and Urbach values are increased from 3.66 to 3.83 eV and 0.28 to 0.45 eV, respectively with increasing film thickness. The extinction coefficient and refractive index were evaluated, and discussed a correlation between the refractive index and the optical bandgap. The real and imaginary dielectric constants, volume/surface energy loss functions and skin depth were deduced. The oscillator energies and parameters were analyzed using the concept of Wemple-DiDomenico and Sellmeier models, respectively for a single oscillator. Static linear refractive index for the studied films exhibits normal dispersion behavior with film thicknesses and satisfied Moss, Ravindra-Gupta, and Herve-Vandamme rules. The linear susceptibility, third-order nonlinear susceptibility and the non-linear refractive index are considerably reduced from 0.20, 29.5 × 10−14 esu, and 5.89 × 10−12 esu with increasing optical band gap energies. The outcomes from the analyses of PPMA demonstrated their potential for usage in electronic, optoelectronic, and non-linear device applications.

Evaluating physiochemical characteristics of tragacanth gum-gelatin network hydrogels designed through graft copolymerization technique

The present work deals with the evaluation of the physiochemical and biomedical properties of hydrogels derived from copolymerization of tragacanth gum (TG) and gelatin for use in drug delivery (DD) applications. Copolymers were characterized by field emission-scanning electron micrographs (FE-SEM), electron dispersion X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. FE-SEM revealed heterogeneous morphology and XRD analysis demonstrated an amorphous nature with short range pattern of polymer chains within the copolymers. The release of the drug ofloxacin occurred through a non-Fickian diffusion mechanism and the release profile was best described by the Korsmeyer-Peppas kinetic model. The hydrogels exhibited blood compatibility and demonstrated a thrombogenicity value of 75.63 ± 1.98 % during polymer-blood interactions. Polymers revealed mucoadhesive character during polymer-mucous membrane interactions and required 119 ± 8.54 mN detachment forces to detach from the biological membrane. The copolymers illustrated the antioxidant properties as evidenced by 2, 2′-diphenylpicrylhydrazyl (DPPH) assay which demonstrated a 65.71 ± 3.68 % free radical inhibition. Swelling properties analysis demonstrated that by change in monomer and cross linker content during the reaction increased the crosslinking of the network. These results suggest that the pore size of network hydrogels could be controlled as per the requirement of DD systems. The copolymers were prepared at optimized reaction conditions using 14.54 × 10−1 molL−1 of acrylic acid monomer and 25.0 × 10−3 molL−1 of crosslinker NNMBA. The optimized hydrogels exhibited a crosslink density of 2.227 × 10−4 molcm−3 and a mesh size of 7.966 nm. Additionally, the molecular weight between two neighboring crosslinks in the hydrogels was determined to be 5332.209 gmol−1.The results indicated that the combination of protein-polysaccharide has led to the development of hydrogels suitable for potential applications in sustained drug delivery.

Evaluation of physiochemical and biomedical properties of psyllium-poly(vinyl phosphonic acid–co-acrylamide)-cl-N,N-methylene bis acrylamide based hydrogels

Present investigation deals with the synthesis of psyllium based copolymeric hydrogels and evaluation of their physiochemical and biomedical properties. These copolymers have been prepared by grafting of poly(vinyl phosphonic acid) (poly (VPA)) and poly(acrylamide) (poly(AAm)) onto psyllium in the presence of crosslinker N,N-methylene bis acrylamide (NNMBA). These copolymers [psyllium-poly(VPA-co-AAm)-cl-NNMBA] were characterized by field emission-scanning electron micrographs (FE-SEM), electron dispersion X-ray analysis (EDAX), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA)- differential thermal analysis (DTG). FESEM, AFM and XRD demonstrated heterogeneous morphology with a rough surface and an amorphous nature. Diffusion of ornidazole occurred with a non-Fickian diffusion mechanism, and the release profile data was fitted in the Korsemeyer-Peppas kinetic model. Biochemical analysis of hydrogel properties confirmed the blood-compatible nature during blood-polymer interactions and revealed haemolysis value 3.95 ± 0.05 %. The hydrogels exhibited mucoadhesive character during biomembrane-polymer interactions and demonstrated detachment force = 99.0 ± 0.016 mN. During 2,2-diphenyl-1-picrylhydrazyl reagent (DPPH) assay, free radical scavenging was observed 37.83 ± 3.64 % which illustrated antioxidant properties of hydrogels. Physiological and biomedical properties revealed that these hydrogels could be explored for drug delivery uses.

Studies on Al-Si based hybrid aluminium metal matrix nanocomposites

A lightweight Hybrid Aluminium Metal Matrix Nanocomposite (HAMNC) is proposed for brake rotor application in this work. Hypereutectic Aluminium-Silicon (Al-Si) grade LM30 alloy is opted as the matrix with Boron Carbide (nB4C) and Rutile (nTiO2) nanoparticles as reinforcements. The brake rotor samples are produced using ultrasonic squeeze-assisted stir-casting, which is cost-effective and feasible for mass production. The hybrid nanocomposite specimens are fabricated by maintaining 1 wt% of nB4C and by varying TiO2 nanoparticles from 0 wt% to 1.00 wt% in steps of 0.25 wt%. The formulations are subjected to microstructure study and dry sliding wear test. The Field Emission Scanning Electron Micrographs (FESEM) reveal that the stir-casting method combining ultrasonic and squeeze effects aids in the uniform distribution of nano reinforcements. The tribological findings show that the hybrid nanocomposite containing 0.75 wt%. of nTiO2 has an 82.76% lower specific wear rate compared to the parent LM30 alloy. Further, the HAMNC brake rotor is 60% lighter than the brake rotors made of Grey Cast Iron making it a potential replacement material.

Structural, electrical, and magnetic characteristics of eco-friendly Dy modified BiFeO3 ceramics

The study of basic crystal structure, dielectrics, magnetic and electrical characteristics of a high temperature sintered dysprosium (Dy) substituted bismuth ferrite (BFO) ceramic material, Bi(Fe0.90Dy0.10)O3 (abbreviated as BFDO10) has been reported in this work. The solid-state reaction (SSR) technique is adopted for synthesizing the material. Study of the X-ray diffraction (XRD) data shows an orthorhombic symmetry. The approximate crystallite size is found to be 29 nm. The field emission scanning electron micrograph (FESEM) shows a high density grains of the sample and energy dispersive X-ray micro-analysis (EDXMA) reveals the presence of its basic components. The extensive analysis of the dielectric and electrical properties of the sample was carried out within a frequency from 1 kHz to 1000 kHz and temperature ranges from 25 to 500 °C. A study of the impedance spectroscopy reveals a negative temperature coefficient of resistance (NTCR) behavior and a non-Debye type of dielectric relaxation process of the compound. The ac-conductivity (σac ) of the material follows Jonscher’s universal power law. A study of the electric field polarization confirms the enhancement in remnant polarization and coercive field. The magnetic property shows an enhancement in ferromagnetic orders by virtue of this doping. Moreover, several other interesting features which could be utilized for modern device applications also specified in this article.

Designing protein-polysaccharides based bioactive copolymeric network by supra-molecular interactions for sustained drug delivery

Keeping in view recent advancements in designing biomaterials from bioactive polysaccharides, the present work deals with the design of protein (gelatin)-polysaccharide (tragacanth gum) based bioactive copolymeric network by supramolecular interactions and covalent linkage for sustained drug delivery (DD) applications. The network copolymeric structure was characterized by field emission-scanning electron micrographs (FE-SEM), electron dispersion X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). FESEM and XRD analyses revealed the heterogeneous morphology of copolymers with an amorphous nature. 13C NMR and FTIR spectra demonstrated the incorporation of poly(acrylamide) (AAm) into network structure by copolymerization reaction. Diffusion of anticancer drug 5-flurouracil (5-FU) occurred in a sustained manner with the Fickian mechanism and was best fitted in first order kinetic model. Polymer-blood interactions revealed the non-hemolytic character of hydrogels. An antioxidant assay evaluated their antioxidant property (26.61 ± 0.85 % of free radical scavenging). Copolymers exhibited mucoadhesiveness during polymer-mucous membrane interactions and required 113.33 ± 5.68 mN detachment forces. Furthermore, the combination of polysaccharide-gelatin has enhanced supramolecular interactions and improved physiological and biomedical properties of network hydrogels. Overall, these properties revealed the suitability of copolymeric hydrogels for drug delivery applications.

Influence of Gd content on structural, electronic, thermoelectric, and optical properties of WO3

WO3-based semiconductor materials are optimistic competitors for modern electronic devices because of their outstanding electronic and optical properties. Simulations on pure and Gd-doped WO3 compositions were executed using Tran and Blaha modified Becke–Johnson approximation. Experimentally, thin films of these compositions were prepared using the chemically derived technique. X-ray diffraction spectra of thin films exhibited cubic structure having space group 221-Pm-3m in all compositions. Field emission scanning electron micrographs reveal the uniform growth of thin films with rod-like compact morphology. The density of states spectra for electronic properties demonstrate the main contribution of W-d and O-p for pure WO3 with p-d hybridization while Gd containing composition provides an additional prominent contribution from f-orbital. Band structure shows an indirect transition for WO3 and band gap values were observed as 1.73 eV which decreased with increment of Gd content. A significant change in thermoelectric parameters was observed with an increment of temperature and Gd doping. The maximum value of the refractive index was observed as 3.02 in the visible energy regime and tends to decrease in Gd containing compositions. The experimentally obtained maximum dielectric constant was observed as 7.89 for pure WO3 and decreased to 4.58 for maximum Gd containing composition. Optical parameters like extinction, absorption coefficient, and optical conductivity show a sharp increment in visible energy region which make these compositions favorable for photovoltaic and optoelectronic applications. The experimentally obtained optical parameters are found in good agreement with simulated results obtained through TB-mBJ approximation.

Preparation and Catalytic Properties of Graphene Oxide/ Phosphotungstic Acid Composites

Background: Cellulose structures are in stable crystallineform. The hydrolysis of cellulose to small reducing sugars is difficult, but essential for its utilization Objective: To investigate the effect of graphene oxide (GO) loading on the catalytic performance of phosphotungstic acid (HPW) for the catalyzed hydrolysis of cellulose, with the purpose to get high yield of total reducing sugar (TRS). Methods: Graphene oxide/phosphotungstic acid (GO/HPW) composites were prepared using a liquid-phase composite method. The materials were applied to catalyze hydrolysis of microcrystalline cellulose in 1-butyl-3-methylimidazole chloride ionic liquid ([Bmim]Cl). The samples were characterized by Powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron micrographs (FE-SEM), pyridine IR and acid-base chemical titration. Results: The Brønsted acidic sites were the main source of acidity in the composites and its concentration was determined to be 0.96 mmol/g. With the use of the GO/HPW composite as catalysts for cellulose hydrolysis, TRS yield of 90.5 % was obtained. Conclusion: GO/HPW composites retained the functional groups of both materials. It was the Brønsted acidic sites in the materials that effectively promoted the cellulose hydrolysis reaction. The structures of GO/HPW with the agglomeration of HPW scattered on GO had high accessibility of acidic sites and fast mass transfer of the reducing sugars to the outside of the catalysts in time to prevent their further conversion into by-products. TRS yield of 90.5 % was obtained from the hydrolysis of cellulose catalyzed by the GO/HPW (1:1.5) composites at 115 ℃ for 4 h using catalysts to cellulose 1:1 ratio.

Surface modifications of TiO2 nanostructured materials induced by 120 MeV Ag ions

The effect of swift heavy ion irradiation on structural, optical, and microstructural properties of TiO2 has been studied. Pellets prepared from TiO2 nanoparticles have been irradiated by 120 MeV Ag ions at different fluences ranging from 5 × 1011 to 1 × 1013 ions cm−2. X‐ray diffraction (XRD), Raman, UV–visible, and photoluminescence (PL) studies indicated anatase phase both in as‐prepared and irradiated pellets. XRD study revealed the crystallite size of the particles as ~16 nm, which is close to the upper limit of the particle size where anatase phase is most stable. Our study thus established the importance of the initial microstructure on the irradiation response of the nanoparticles. Though irradiation did not affect the crystal structure and the polycrystalline nature of the anatase TiO2, it suppressed the crystalline volume fraction. Poisson fitting of the suppression of XRD peak area with irradiation fluence revealed radius of the track of each 120 MeV Ag ion in TiO2 nanoparticles as ~2.1 nm. Irradiation, in addition to creating disorder, darkened the surface of the pellets because of the creation of oxygen vacancies in the TiO6 octahedra. Reorganization of these defects led to suppression of the band gap of TiO2 nanoparticles from 3.19 eV of the pristine sample to 3 eV for samples irradiated beyond a critical fluences 3 × 1012 ions cm−2. The size of the nanoparticles and their agglomeration remained unaffected by irradiation as indicated by field emission scanning electron micrographs.

Novel TiO2-based memristors FET with programmable SET/RESET for neuromorphic computing

TiOx switching oxide-based gated memristor FET is fabricated using a sputtering and lift-off process. 3 µm wide source-drain electrode covered by ∼ 15 nm TiOx layer. Field emission scanning electron micrograph confirms the FET structure. 6.1 V forming voltage is essential to initiate the switching process. The positive and negative gate voltage effect on the set and reset process was confirmed. The gate-controlled memristor device can open another option for the synaptic process.

Infrared-to-visible conversion in strontium sulphate through a defect-based infrared stimulated visible emission phenomenon.

Strontium sulphate (SrSO4 ) is a defect-based photoluminescence material, generally used in thermoluminescence applications, and has been studied for infrared (IR) stimulated visible emission. The SrSO4 particles were synthesized using a precipitation method. The orthorhombic phase of SrSO4 was confirmed from the X-ray diffraction pattern and the formation of micron-sized particles was authenticated from field emission scanning electron micrographs. The elemental composition of oxygen and strontium was determined using energy-dispersive X-ray analysis measurement that confirmed the presence of and intrinsic defects in the material. Photoluminescence investigations showed the presence of various defect bands in the band gap giving rise to intrinsic luminescence in SrSO4 . The emission in the visible region was attributed to the defect band arising due to . Photoluminescence lifetime measurement confirmed the presence of stable defect states with a lifetime in microseconds. The SrSO4 sample was tested using IR lasers and a red-orange emission spot was observed from the powder sample when excited with IR lasers. The underlying principle for IR-to-visible conversion in the material is a defect-mediated phenomenon that has been described through the energy level diagram of the material.

Structure, magnetic morphology and magnetization correlations in pulsed laser deposited CoFe[formula omitted]O[formula omitted] ([formula omitted]) thin films

The present paper reports a complete study on the correlation between structure, morphology, and magnetic properties of (111)-oriented cobalt ferrite (CoFe2O4) thin films with varying film thickness. The CoFe2O4 (CFO) thin films were deposited on Pt-coated Si substrate by pulsed laser deposition (PLD) at 550 °C. The x-ray diffraction (XRD) data confirms the (111)-oriented growth of the cobalt ferrite films. The in-plane morphology of the films in the field emission scanning electron micrographs ensure the Stranski–Krastanov growth mechanism, and the atomic force micrographs confirms the effect of lattice relaxation on the morphology of the films with varying thickness. The possible cation distributions for the samples were determined from the Raman spectroscopy, which revealed the crystal structure-magnetic property correlations in cobalt ferrite films. The magnetic hysteresis (M−H) loops show a significant spin reorientation by showing the variation between the in-plane (IP) and out-of-plane (OP) magnetization. The presence of a kink on the OP M−H loops and its variation with film thickness clearly establishes the existence of competing magnetic anisotropies in the films. The high coercivity (HC) values observed for OP magnetization of cobalt ferrite films with thicknesses 115 nm and 125 nm may be explored for possible room-temperature (RT) device applications.

Electrochemical behavior of ECAP-processed Sn–5Sb alloy

An attempt has been made in this research to evaluate the effects of severe plastic deformation (SPD) on the electrochemical and passivation response of Sn–5Sb alloy. The electrochemical response of severely deformed alloy through the equal channel angular pressing (ECAP) process has been studied by cyclic voltammetry (CV), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and Mott–Schottky in 0.1 M NaOH solution. The grain structure and corrosion product of samples have been evaluated by X-ray diffraction (XRD), atomic force microscopy (AFM) patterns, transmission electron microscopy (TEM), and field emission scanning electron (FESEM) micrographs. It has been revealed that imposing such a large strain yields specimens with finer grain structure resulting in higher corrosion resistance and higher protecting passive films.

Surface morphology and optical properties of thin films of plasma polymerized methyl acrylate

Thermally stable plasma polymerized methyl acrylate (PPMA) thin films are fabricated onto spotless glass substrates by AC power plasma polymerization technique. Field emission scanning electron micrographs of these films exhibit clusters/agglomerations on the surface. Energy dispersive x-ray analysis confirms the existence of 52.38, 52.63 and 51.55% of carbon and 47.62, 47.31 and 46.45% of oxygen, respectively in 170, 230 and 290 nm thick PPMA films. The molecular vibrations of various natures observed by attenuated total reflectance Fourier transform infrared spectroscopy of methyl acrylate and PPMA represent that the percentage of hydrophilic groups is smaller than the hydrophobic groups. Thermogravimetric analyses demonstrate that the major weight loss occurs in the temperature range from 500 to 850 K. Ultraviolet–visible spectroscopy demonstrates that the allowed direct energy band gap varies from 3.77 to 3.83 eV, whereas the indirect energy band gap alters from 3.40 to 3.48 eV with film thicknesses from 120 to 290 nm. Other optical parameters such as Urbach energy, refractive index, optical extinction coefficient, dielectric constants, quality factor, and skin depth have also been investigated for the PPMA thin films to elucidate their suitability in optoelectronic devices.

An ab initio DFT perspective on experimentally synthesized CuBi2O4.

Here we present a comprehensive density functional theory (DFT) based ab initio study of copper bismuth oxide CuBi2O4 (CBO) in combination with experimental observations. The CBO samples were prepared following both solid-state reaction (SCBO) and hydrothermal (HCBO) methods. The P4/ncc phase purity of the as-synthesized samples was corroborated by Rietveld refinement of the powdered X-ray diffraction measurements along with Generalized Gradient Approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and the Hubbard interaction U corrected GGA-PBE+U relaxed crystallographic parameters. Scanning and field emission scanning electron micrographs confirmed the particle size of the SCBO and HCBO samples to be ∼250 and ∼60 nm respectively. The GGA-PBE and GGA-PBE+U derived Raman peaks are in better agreement with that of the experimentally observed ones when compared to local density approximation based results. The DFT derived phonon density of states conforms with the absorption bands in Fourier transform infrared spectra. Both structural and dynamic stability criteria of the CBO are confirmed by elastic tensor and density functional perturbation theory-based phonon band structure simulations respectively. The CBO band gap underestimation of GGA-PBE as compared to UV-vis diffuse reflectance derived 1.8 eV was eliminated by tuning the U and the Hartree-Fock exact-exchange mixing parameter αHF in GGA-PBE+U and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals respectively. The HSE06 with αHF = 14% yields the optimum linear optical properties of CBO in terms of the dielectric function, absorption, and their derivatives as compared to that of GGA-PBE and GGA-PBE+U functionals. Our as-synthesized HCBO shows ∼70% photocatalytic efficiency in degrading methylene blue dye under 3 h optical illumination. This DFT-guided experimental approach to CBO may help to gain a better understanding of its functional properties.

Wound healing efficacy of curcumin-loaded sandalwood bark-derived carbon nanosphere/PVA nanofiber matrix.

The present investigation deals with the evaluation of the wound healing efficacy of sandalwood bark-derived carbon nanospheres loaded with curcumin-embedded polyvinyl alcohol (PVA) nanofiber membranes (NF). Carbon nanospheres (CNS) were prepared by pyrolyzing sandal wood bark powder at 750 °C. The morphology was confirmed by field emission scanning electron micrographs and a rich amount of carbon was confirmed by the energy dispersive X-ray technique. Curcumin, an active wound healing drug was loaded onto synthesized CNS and confirmed by ATR-IR studies. Drug-loaded CNS were anchored in a PVA matrix via electrospun nanofiber fabrication. The fabricated nanofiber membranes were characterized and evaluated for wound healing efficiency. The cytotoxicity assay proved the non-toxic nature of the prepared PVA/CNS-curcumin-loaded NF. Membranes with active CNS/drug showed better antimicrobial activity against S. aureus and E. coli, which was estimated using the zone of inhibition (ZOI) test. The in vitro scratch wound healing assay of prepared PVA/CNS-curcumin nanofibers was efficient enough and showed 92 to 98% wound closure, which was greater than the control (without drug) nanofiber membranes. The PVA nanofiber matrix with interconnected structure and carbon nanostructures together enhanced the wound healing efficacy of the considered wound healing membrane, which is a promising novel approach for future wound healing patches.

Optical Properties, Microstructure, and Phase Fraction of Multi-Layered Monolithic Zirconia with and without Yttria-Gradient.

The differences in the optical properties of multi-layered zirconia with and without yttria-gradient are not fully understood. This study aimed to evaluate and compare the optical properties, related microstructures, and phase fractions of multi-layered zirconia with and without yttria-gradient. For this, multi-layered zirconia of 5 mol% yttria (5Y) stabilized (Katana STML) and 4Y/5Y stabilized (e.max MT Multi) were cut layerwise, sintered, and analyzed using the opalescence parameter (OP), average transmittance (AT%), translucency parameter (TP), and contrast ratio (CR). The average grain size and phase fractions were obtained from field-emission scanning electron micrographs and X-ray diffraction patterns, respectively. Although the TP values of Katana STML and e.max MT Multi did not show a significant difference (except for transition layer 1), the results of AT and CR showed that the translucency of e.max MT Multi was slightly higher than that of Katana STML (p < 0.05). The opalescence gradient was higher in Katana STML than in the e.max MT Multi. In both zirconia types, translucency increased from the dentin to enamel layer based on the AT, TP, and CR results, while OP decreased (p < 0.05). The higher translucency from the dentin to enamel layer in Katana STML was caused by the pigmentation gradient, while in e.max MT Multi, it was caused by the difference in phase fraction and the pigmentation gradient.