Increment Of Particle Size Research Articles

Improving the performance of biobased polyurethane dispersion by the incorporation of photo-crosslinkable coumarin

High biobased carbon content polyurethane dispersions (PUD) are a more sustainable alternative to conventional oil-derived waterborne dispersions in coatings. However, there are still many performance limitations from restricted availability of effective renewable monomers and oligomers. This work demonstrates the improvement of the properties of high biobased content PUD and derived coating by introducing a photo-reversibly crosslinkable coumarin as chain extender within the structure. The effect of partial substitution of 1,3-propanediol biobased by a di-hydroxy photo-reactive cyclic coumarin on the particle size and the stability was analyzed by dynamic light scattering (DLS) and multiple light scattering (MLS). The lateral and more rigid structure of coumarin involved a moderated increment in particle size without significant effect on the dispersion stability for at least 45 days. Associated improvement in hardness and toughness was also demonstrated by tensile test, pendulum hardness, pencil hardness and scratch resistance test. Furthermore, controlled UV irradiation of the polyurethane gave rise to a mechanical performance adjustment from reversible photo-crosslinking and scission of the coumarin molecules within the macromolecular structure. A 70% dimerization degree of the coumarin within the polyurethane film by UV light provided a partially reversible threefold higher tensile strength than that of the original biobased formulation as an effective tool to tune the response of biobased polyurethanes.Graphical

Structural phase transition and charge carrier dynamics in Dy containing La6MoO12 ionic conductor

The solution combustion method was adopted to prepare a single-phase La6MoO12 compound by doping 10% Dy in the La site and sintered at 800 °C, 1000 °C, and 1200 °C temperatures. The X-ray diffraction patterns confirmed a phase transition of the samples from the cubic fluorite phase (Fm3‾m) to a complex rhombohedral structure (R3‾m) with increasing sintering temperature. The microstrain and particle size show the opposite behaviour in the case of 800 °C and 1200 °C sintered samples. The FE-SEM and XRD results corroborated the increment of particle size with sintering temperature. Elemental mapping confirmed the uniform distribution of elements in the compositions. Red and blue shifts in optical bandgap were observed with sintering temperature. All samples show a negative temperature coefficient of resistance (NTCR) behaviour. The sample sintered at 1200 °C has the highest ionic conductivity of 1.03×10−4Ω−1cm−1 at 540 °C. The reciprocal temperature dependence of conductivity followed the VTF equation. The dielectric loss tangent indicated that all samples have a single relaxation process. The time-temperature superposition principle has been verified from the scaling of the dielectric loss tangent.

Viscosity of CuO nanofluids: Experimental investigation and modelling with FFBP-ANN

The current work examines the viscosity of nanofluids as a function of nanoparticle concentration, size, and temperature. CuO nanoparticles with an average size of 15 nm, 45 nm, and 75 nm have been used in this study. Viscosity measurements of volume concentrations of 1% to 4% are carried out in the temperature range of 293 K to 353 K. The results show a maximum increase of 23% in effective viscosity due to the addition of nanoparticles. However, the viscosity decreases by about 80% as the temperature increases from 293 K to 353 K. Furthermore, a maximum increase of 0.5% in viscosity is observed with the particle size increment. Based on present experimental data and literature data, a correlation is developed to predict the effective viscosity. Furthermore, ANN modelling is carried out to predict the effective viscosity of nanofluids and compared with the developed correlation. The results demonstrate that ANN modelling outperforms hypothesised correlation in estimating the effective viscosity. The R-squared values for the ANN model and correlation model are 0.95 and 0.90, respectively.

Size distribution evolution and viscosity effect on spherical submicrometer particle generation process by pulsed laser melting in liquid

Spherical submicrometer particles (SMPs) can be fabricated by pulsed laser melting in liquid (PLML). In this process, raw nanoparticles dispersed in liquid are irradiated by a pulsed laser, heated over the melting point to generate molten droplets, and quenched to form SMPs. The particle size increment is caused by aggregating and merging raw particles in liquid by transient heating. In this study, the viscosity effect on the formation process of SMPs by PLML process is studied by changing aqueous glycerin solution concentration. In highly viscous liquid, smaller SMPs are generated due to the ineffective aggregation process. The temporal evolution of cumulative volume frequency of particles can be simulated, considering the constraints of the non-melting at larger size due to high heat capacity and evaporation for smaller particles by overheating. The SMP size can be controlled by viscosity of the liquid, prior disaggregation time, and liquid temperature.

Fabrication of edible solid lipid nanoparticle from beeswax/propolis wax by spontaneous emulsification: Optimization, characterization and stability

In the current study, the production and characterization of novel solid lipid nanoparticles (SLNs) using safe/low-cost natural beeswax (BW) and propolis wax (PW) and by the simple and inexpensive assay of spontaneous emulsification were studied. To fabricate SLNs, the optimum levels of surfactant/oil ratio (SOR), stirring speed, and time were obtained based on minimum particle size (PS) and polydispersity index (PDI). Therefore, the optimal conditions to produce PW and BW nanoparticles were SOR of 1.26 and 2 under stirring speed of 1050 rpm for 20 min, leading to PS of 21.9 and 23.2 nm, respectively. The contact angle of 73.7° and 62.9° for BW and PW SLNs respectively, showed suitable hydrophilicity to stabilize oil-in-water (O/W) Pickering emulsions. Temperatures over 70 °C led to a drastic increment of PS in both types of SLNs. Upon nanoparticles drying, the utilization of cryoprotectants could cause less aggregation and better reconstitution.

Analysis of the heat conduction mechanism for Al2O3/Silicone rubber composite material with FEM based on experiment observations

Based on the microcosmic configuration of samples on cross-section, a three-dimensional particle random distribution model of spherical Al2O3/SIR composites was built. Through sample measurement and model calculation, the effects of volume fraction, particle size and binary filling schemes of the Al2O3 fillers on thermal conductivity of the composites were studied. The particle contact probability which aiming at single sized particles filling case and different sized particles filling case were proposed to quantitatively characterize the formation probability of heat conduction path in the materials. Increasing the volume fraction of fillers can increase the contact probability of filler particles. When the volume fraction of Al2O3 fillers exceeds a certain threshold, the thermal conductivity of composites increases slightly first and then decreases with the increment of particle size. For Al2O3/SIR composites filled with different particle size fillers, as the volume fraction of the reinforced fillers with small particle size increases, the thermal conductivity of composites rises. As the particle size of the reinforced fillers increases, the thermal conductivity rises first and then reduces. The optimal volume ratio between the main fillers and reinforced fillers will be affected by the total filling content of the Al2O3 fillers.

Intriguing photophysical aspects of nitro substituted 2-(2′-hydroxyphenyl)benzothiazole (HBT) derivative: AIE in non-polar media?

Abstract Excited photophysics of a synthesized molecule namely 2-(benzo[d]thiazol-2-yl)-5-nitrophenol (BTNP) have been studied using steady state and time resolved techniques. BTNP exhibits ESIPT exclusively in non-polar media with exceptional Stokes’ shift. In polar solvents anion formation of BTNP hampers the ESIPT process. Solid state emission spectral pattern matches reasonably well with that in non-polar medium. Dynamic light scattering showed the increment of particle size in heptane in comparison to water, a trend reversed to conventional trait of Aggregation Induced Emission (AIE) active molecules. Nitro substituent in BTNP reverses the conventional definition of a ‘good solvent’ and ‘bad solvent’, thereby promoting ESIPT in non-polar medium via aggregation. As all reports on AIE active compounds claim water to be the solvent capable of producing the effect, we have reversed the effect by simple change in substitution. Reversal of AIE phenomenon would certainly open up new avenues in future research on AIE active fluorophores.

Photocatalytic performances of cobalt sulfides prepared by solution combustion synthesis using mixed fuels

Cobalt sulfide powders (CoS, Co9S8 and CoS1.97) were synthesized by solution combustion method using conventional and microwave heating routes. The powders were obtained using cobalt nitrate as both cobalt source and oxidizer together with proper amounts of thiourea as sulfidizing agent and glycine as an auxiliary reductant. Effects of thiourea and glycine amounts in conjunction with the type of combustion route, on the phase constituents, microstructure and optical properties were studied using infrared spectroscopy, thermal analysis, X-ray diffractometry, electron microscopy and diffuse reflectance spectrometry techniques. The results revealed that single phase cobalt sulfides can be delivered by precise adjustment of thiourea and glycine amounts and a proper heating (conventional or microwave) route. Co9S8 single phase was obtained using equal amounts of thiourea and glycine by both microwave and conventional heating modes. Using thiourea/glycine ratio of 1.5, leads to the formation of CoS1.97 single phase by conventional heating, while CoS was obtained when microwave heating was applied. Increasing the amount of thiourea caused particle size increment. Maximum photocatalytic degradation efficiency (89 and 89.5%) of methylene blue was obtained at pH = 9 for microwave combusted samples. Quenching tests in the presence of •OH− radical scavenger (isopropyl alcohol) showed that the major oxidizing species were • OH− radicals.

The crystalline structure of gadolinium oxide nanoparticles (Gd2O3-NPs) synthesized at different temperatures via X-ray diffraction (XRD) technique

Sol-gel is an effective method in producing nanoparticles with high purity and crystallinity. Herein, we report the synthesis of gadolinium oxide nanoparticles (Gd2O3-NPs) via sol-gel technique with an emphasis on the effect of temperature on the crystallization process of the nanoparticles. Gd2O3-NPs were prepared from gadolinium chloride hexahydrate precursor (GdCL3.6H2O) and ethylene glycol (EG). The Gd2O3-NPs were synthesized at different annealing temperatures of 500 °C, 700 °C, 900 °C, 1000 °C and 1100 °C. The X-ray diffraction (XRD) analysis revealed that the sample was crystalline with a cubic phase, achieving optimum crystallinity (82.3%) at an annealing temperature of 1000 °C. The Williamson-Hall (W–H) analysis and size-strain plot (SSP) method demonstrated that the strain decreases with the increment of particle size. Whereby the strain and average particle size of Gd2O3-NPs synthesized at the temperature of 1000 °C were 0.00053 and 62.96 nm respectively. Further investigation by transmission electron microscopy (TEM) indicated that the Gd2O3-NPs is a single-crystal with approximately polycrystalline shapes. The particle size ranges from 38.01 ± 5.9 nm, 49.29 ± 7.41 nm, 60.58 ± 6.7 nm and 74.34 ± 9.3 nm per annealing temperature of 700 °C, 900 °C, 1000 °C and 1100 °C respectively. Whereas, via field emission scanning electron microscopy (FESEM), synthesized Gd2O3-NPs were uniform and had spherical-like morphology with an average diameter of 40.71 ± 4.5 nm, 52.92 ± 6.9 nm, 65.00 ± 7.02 nm and 73.56 ± 10.04 nm at different annealing temperatures of 700 °C, 900 °C, 1000 °C and 1100 °C respectively. The results obtained showed that the mean particle size of the Gd2O3-NPs estimated from the TEM, FESEM, W–H analysis and SSP method were intercorrelated. In terms of molecular conformation, Fourier transform infrared spectroscopy (FTIR) peaks at 448 cm−1 and 546 cm−1 affirms the formation of the Gd2O3-NPs, whereby these peaks corresponds to the Gd–O stretching frequencies of Gd2O3 cubic phase when samples were heated at 700 °C - 1100 °C. It is envisaged that the sol-gel technique is promising in synthesizing Gd2O3-NPs for various possible applications, potentially as a contrast agent for magnetic resonance imaging (MRI).

Process Optimization of Curcumin-Loaded Coconut Oil and Honey Nanoemulsion for Better Skin Permeation

This study was focused on the optimization of preparing a curcumin-loaded coconut oil and honey nanoemulsion using a low energy emulsifying technique. Curcumin is a bioactive compound with low bioavailability and stability. Response surface methodology (RSM) with Box Behnken design was used to optimize the base formulation based on the three independent variables such as honey (1–3%), virgin coconut oil (1.0–1.5%) and Tween 80 (5.0–9.0%) to obtain low particle size (10.11[Formula: see text]nm), polydispersity index (0.27) and turbidity (0.24–1.11) system. Subsequently, the second optimization was carried out after curcumin was loaded into the base formulation. Another three independent variables such as polyethelene glycol (0.8–1.5%), curcumin (0.01–0.1%) and honey (1.8–2.4%) were used to produce the nanorange of particle size (14.32[Formula: see text]nm), narrow polydispersity index (0.152), and high encapsulation efficiency (98.0%). The curcumin-loaded nanoemulsion was found to have high stability with only 8.5% increment in particle size after storage for three months at 4∘C and 45∘C. The radical scavenging activity of encapsulated curcumin in nanoemulsion was decreased ([Formula: see text]%) compared to free curcumin. Nanoemulsion appeared to increase in vitro release rate of curcumin by about 42%, especially for the first 2[Formula: see text]h in Franz diffusion cell using rat skin.

Study on processing stability and fermentation characteristics of donkey milk

The aim of this study was to investigate the effect of different processing treatments, including heating, ultrasonic treatment and fermentation on the stability of donkey milk. In general, the donkey milk performed stable when lower level of heat treatment and ultrasonic treatment were applied. Excessive thermal treatment (>85 °C) decreased intensity of protein bands (15, 30 and 70 kDa) as observed from Sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE). Caseins were sensitive to ultrasonic treatment, whereas the whey proteins were more stable under ultrasonic treatment. Centrifugal precipitation rate and surface hydrophobicity were increased after heating and ultrasonic treatment. In addition, an increment of particle size was detected with temperature higher than 85 °C was applied. No significant effects were observed on zeta potential and particle size of donkey milk after ultrasonic treatment. Fermentation allowed donkey milk to form a gel with poor textural properties but with high peptide content. The highest peptides content was obtained by using L. helveticus LZ-R-5 and Lactobacillus helveticus MB2-1.

Tunable birefringence in silica mediated magnetic fluid

The present study reports magnetic and optical properties of silica mediated lauric acid stabilized magnetic fluids. The tunable birefringence (Δn) and other properties are investigated as a function of (i) concentrations of silica suspension, and (ii) saturation magnetization (MS) 0.5099 kA m−1 (FN30) and 1.2855 kA m−1 (F30) of magnetite magnetic fluid (MF). The study reveals that Δn suppresses on addition of silica in FN30, whereas enhances (up to critical concentrations of silica) in F30. The magnetic field induced chain observed in the FN30 based fluids are long, thick and scattered, while short, thin and dense chains emerges in F30 based fluid. The magnetic field induced assembly and the magnetic parameters correlates with the results of Δn. The particle size analysis indicates increment of particle size on addition of silica nanoparticles. The thermogravimetry analysis confirms the direct interaction of silica nanoparticles and the lauric acid coated magnetite particles. This is the first report of direct interaction of silica—magnetite magnetic fluids, and its subsequent effect on tunable birefringence and other properties.

Heat treatments of defatted soy flour: Impact on protein structure, aggregation, and cold-set gelation properties

Abstract This study reveals that mild heat treatments of defatted soy flour promote Maillard reaction and modify its protein techno-functional properties such as solubility, aggregation, and cold-set gelation. Glycation was promoted by treatments of defatted soy flour (DSF) at 60 °C for 12, 24, and 48 h, with and without relative humidity control (RHC and WRHC, respectively) at 79%. All samples presented a significant increase of glycation extent (GE), reaching the highest value after 48 h at RHC. Despite all samples presented a similar protein denaturation degree, the increase in GE was accompanied by a decrease of antitryptic activity. Protein solubility (PS) of DSF remained constant for treated samples WRHC. However, PS decreased progressively with the treatment time at RHC. SDS-PAGE of soluble proteins revealed a positive relation between band intensities and PS. Despite sample dispersions showed a protein particle size increment with treatment time, further aggregation after heat-treatments at 100 °C produced a similar protein size distribution among samples. Rheological and microstructural studies of cold-set gels of samples obtained WRHC revealed no changes in the maximum elastic modulus (G’max) and a slight increase of its pore sizes. However, samples obtained with RHC showed cold-set gels with a progressive G’max decrease with the treatment time, which could be related to a coarser gel microstructure. In the more extreme condition, the sample obtained after 48 h at RHC showed a total loss of gelation capability. These results can be used to address the development of new tofu-like food products with different rheological properties.

Synthesis of Carbon Nanotubes from Industrial Wastes Following Alkali Activation and Film Casting Method

In the present study, synthesis, and characterization of carbon nanotubes (CNTs) has been carried out using fly ash, red mud, and rock sample as raw and filler material. The feed stock was used for the fabrication of bio-composite films of polyvinyl alcohol. Pyrolysis of bio-composite film produced by aqueous casting method was performed at 500 °C. The increment in particle size of the modified samples was analysed using laser particle size analyser. Oxide based composition and elemental analysis of the samples was reported using XRF. The comparison between crystalline phase and various organic and inorganic bonds present before and after modification were analysed using XRD and FTIR, respectively. The resultant carbon nanotubes were analysed for structural, morphological, and thermal stability using FESEM, TEM, Raman spectroscopy, and thermogravimetric analysis. Total pore volume, specific surface area, and the respective pore size distribution of the carbon nanotube mixture were analysed through BET analysis. Magnetic character of synthesized CNTs was analysed by using vibrating sample magnetometer. The obtained results from different characterization techniques shows successful preparation of CNTs with superior magnetic properties.

Aqueous asymmetric supercapacitors based on ZnCo2O4 nanoparticles via facile combustion method

ZnCo2O4 (ZCO) nanoparticles are synthesized via a facile, fast and cost-effective combustion method. The effect of calcination temperature is studied on the morphology, crystallite size and electrochemical properties of the ZCO. Scanning electron microscope observation reveals that the calcination temperature strongly influences the morphology of the prepared ZCO. At the calcination temperatures of 300, 400 and 600 °C, the ZCO samples show the specific capacitance values of 202, 668 and 843 F g−1, respectively with the current density of 1 A g−1. Furthermore, higher calcination temperature (800 °C) leads to rapid increment of particle size, low specific capacitance (432 F g−1 at 1 A g−1) and inferior rate capability of ZCO, which may be related to the severe micro-strain and crack formation upon repeated electrolytic ions during charging-discharging process. Owing to the excellent specific capacitance of the ZCO (prepared at 600 °C), its performance is further investigated in asymmetric supercapacitor (ASC) device and a high energy density of 26.28 W h kg−1 is obtained at the power density of 716 W kg−1 under the current density of 1 A g−1. Parallel-connected 14 light-emitting diodes are lit up from series-connected two ASCs. In addition, a motor fan is powered by the two ASCs. In the light of the above results, the ZCO nanoparticles may be expected to be a prospective viable electrode material for high-performance supercapacitors.

Size dependent morphology, magnetic and dielectric properties of BiFeO3 nanoparticles

AbstractNano-sized BiFeO3 were synthesized by sol-gel auto combustion method and report the effect of different annealing temperature (400 °C, 500 °C, 600 °C) on phase formation, morphology, magnetic and dielectric properties of synthesized bismuth ferrite (BiFeO3) nanoparticles. The phase formation of BFO nanoparticles were confirmed by X-ray diffraction pattern. Further, significant increment in particle size with increasing annealing temperature was estimated by field emission electron microscopy (FESEM). Magnetization curve showed the soft ferromagnetic behavior of the samples annealed at 400 OC and 500 OC that was explained on the basis of disturbance of spiral modulated long range antiferromagnetic order of bulk BFO. Dielectric response revealed decrease in dielectric constant with increasing annealing temperature. BFO is a room-temperature multiferroic material so it is potential candidate for various applications viz. Water waste treatment, gas sensors and photovoltaic cells in rural areas.

Growth and Magnetic Behaviours of La0.7Sr0.3MnO3 Nanoparticles Synthesized via Thermal Treatment Method

La0.7Sr0.3MnO3 (LSMO) nanoparticles were synthesized by thermal treatment method using water as solvent and polyvinyl pyrollidone (PVP) as capping agent. The as prepared precursor was calcined at various temperatures ranging from 500°C to 1000°C. Structural characterization using X-rays diffractions (XRD) showed that the LSMO nanoparticles, calcined at temperature ≥ 600°C, have single phase of La0.7Sr0.3MnO3 with rhombohedral crystal structure without any secondary phases being detected. The average particle size of nanoparticles increased gradually from 23 to 163 nm for samples calcined at 500 to 1000°C. Magnetic measurement at room temperature using vibrating sample magnetometer (VSM) indicated that the LSMO nanoparticles had soft ferromagnetic behaviour with coercivity ranged from 3.43 to 33.78 G. The magnetic saturation (Ms) of nanoparticles increased with the increment of particle size. From Electron Spin Resonance (ESR) measurement, the g-value of LSMO nanoparticles increased with the increasing of calcination temperature. The ESR indicated a coexistence of ferromagnetic and paramagnetic phases in LSMO nanoparticles below Curie temperature (Tc). The Tc was in the range of 50-80°C for LSMO calcined at 500°C and it is in the range of 80-110°C for LSMO calcined 600, 700, 800, 900, and 1000°C.

Correlation between photoelectrochemical and photoluminescence measurements of Ag-doped ZnO/ITO photoanode

Silver-doped zinc oxide (SZO) thin films have been deposited onto indium-doped tin oxide substrates (ITO) using sol–gel spin-coating technique with different Ag doping content (1, 2 and 5% Ag). The effect of silver incorporation on structural, morphological, optical and photoelectrochemical (PEC) properties of the SZO films was investigated. Ag incorporation resulted in an enhanced grain size and thickness of elaborated SZO films. Scanning electron micrographs exhibited a uniform distribution of spherical grains with particle size increment after doping. Band gap energies were found to increase after Ag doping. Photoluminescence (PL) measurements revealed that the energy band gaps of the films were in the UV region. As compared to pure ZnO thin film, the samples are more photoactive, and the film containing 2% Ag yielded the highest photocurrent. A correlation study between PEC and PL measurements of Ag-doped ZnO/ITO photoanode leads to a reverse variation. Charge transfer processes at the ZnO–electrolyte interface were identified by electrochemical impedance spectroscopy.

Nonlinear absorption and optical limiting of Ag–CdSe nano-hybrids of different growth times

Metal-semiconductor Nano-composites have enormous applications due to Plasmon –exciton coupling. Open aperture Z-scan is investigated for Ag–CdSe hybrid nanostructure, a toggle from saturable absorption process SA to reverse saturable absorption RSA is observed upon laser power increment. Proofs of crystal and morphological structure are given by selected area electron diffraction (SAED) and high resolution transmission electron microscope (HRTEM). Red shifting in photoluminescence spectra PL is observed which is ascribed to the particle size increment. Intriguing nonlinear findings can be used to engineer optical switching devices and optical limiters.

Exploration of charge carrier delocalization in the iron oxide/CdS type-II heterojunction band alignment for enhanced solar-driven photocatalytic and antibacterial applications.

Recyclable magnetic photocatalysts of iron oxide (IO)/CdS core/shell nanocrystals (CSNCs) were prepared by a facile sequential one-pot method using 3, 3'-thiobispropanoic acid (TDP) as a bridge. The CSNCs showed redshift in absorption edge, decrease in the optical band gap, reduced exciton decay rates and increment in particle size. Quenching studies have been employed to understand the position of the electron/hole wave-functions at the IO/CdS interface. Antimicrobial tests have also been performed using broth tube dilution and disc diffusion methods against S. aureus. Additionally, photocatalytic properties of IO/CdS CSNCs have been evaluated for the decomposition of xylenol blue. In comparison with CdS quantum dots (QDs) and iron oxide nanoparticles (IONPs), the IO/CdS CSNCs showed improved photocatalytic and bactericidal activities. Finally, levels of oxidative damage to proteins and lipids were evaluated.