Crystalline Type Research Articles

Retrogradation, gel texture properties, intrinsic viscosity and degradation mechanism of potato starch paste under ultrasonic irradiation

The effects of sonication on the retrogradation, gel texture properties, intrinsic viscosity and degradation of potato starch paste (PSP) were investigated using a specially designed reactor to study changes in molecular structure and functional properties. The retrogradation was analyzed by an x-ray diffractometry. The gel texture properties were analyzed by texture profile analysis (TPA) and the intrinsic viscosity was analyzed using a Cannon-Ubbelohde viscometer at different sonication times, intensities and PSP concentrations. The molecular weight of PSP was determined using gel permeation chromatography (GPC). The results showed that retrogradation of PSP occurred when it was placed in a high density ultrasonic field, and was accompanied by a transition from crystalline type B to type VH. The TPA results indicated remarkable decreases in gel texture properties (hardness, fracture ability, adhesiveness, gumminess, and chewiness) when the sonication time was prolonged, the intensity was increased and when the PSP concentration was reduced. Intrinsic viscosity decreased with extended sonication time and at higher intensity, but increased as the PSP concentration increased. The GPC results showed that the average molecular weight of PSP decreased significantly upon ultrasonic irradiation and the sample had a narrower distribution of molecular weight. The degradation kinetics were adequately described by the Baramboim models. Radical trapping by 2,2-diphenylpicrylhydrazyl was used to assess the radical-attack mechanism in PSP subjected to ultrasound. Under the reaction conditions, degradation of PSP in the ultrasound field is caused by OH radicals and mechanochemical effects. Mechanochemical effects were the main cause of bond scission.

Ordered Mesoporous NiCo2O4 Nanospheres as a Novel Electrocatalyst Platform for 1-Naphthol and 2-Naphthol Individual Sensing Application.

The novel ordered mesoporous NiCo2O4 (meso-NiCo2O4) nanospheres were synthesized by the nanocasting strategy followed by a calcination process for 2-naphthol (2-NAP) and 1-naphthol (1-NAP) individual sensing application. The as-obtained meso-NiCo2O4 material possesses mesoporous structure in spinel crystalline type with a larger specific surface area than other structures. The meso-NiCo2O4-modified carbon paste electrode exhibited excellent electrocatalytic performance for NAP detection by amperometry measurement. The fabricated sensor of 2-NAP and 1-NAP has a wide linear detection range (0.02-300 and 0.02-20 μM) with high sensitivity (1.822 and 1.510 μA μM-1 cm-2) and low limit of detection (0.007 and 0.007 μM), respectively. In addition, the NAP sensors possess excellent reproducibility, stability, and selectivity.

Production and Characterization of Bulk MgB2 Material made by the Combination of Crystalline and Carbon Coated Amorphous Boron Powders

The object of this investigation is to reduce the cost of bulk production and in the same time to increase the critical current performance of bulk MgB2 material. High-purity commercial powders of Mg metal (99.9% purity) and two types of crystalline (99% purity) and 16.5 wt% carbon-coated, nanometer-sized amorphous boron powders (98.5% purity) were mixed in a nominal composition of MgB2 to reduce the boron cost and to see the effect on the superconducting and magnetic properties. Several samples were produced mixing the crystalline boron and carbon-coated, nanometer-sized amorphous boron powders in varying ratios (50:50, 60:40, 70:30, 80:20, 90:10) and synthesized using a single-step process using the solid state reaction around 800 °C for 3 h in pure argon atmosphere. The magnetization measurements exhibited a sharp superconducting transition temperature with Tc, onset around 38.6 K to 37.2 K for the bulk samples prepared utilizing the mixture of crystalline boron and 16.5% carbon-coated amorphous boron. The critical current density at higher magnetic field was improved with addition of carbon-coated boron to crystalline boron in a ratio of 80:20. The highest self-field Jc around 215,000 A/cm2 and 37,000 A/cm2 were recorded at 20 K, self-field and 2 T for the sample with a ratio of 80:10. The present results clearly demonstrate that the bulk MgB2 performance can be improved by adding carbon-coated nano boron to crystalline boron, which will be attractive to reduce the cost of bulk MgB2 material for several industrial applications.

Quasicrystalline and crystalline types of local protein order in capsids of small viruses

Like metal alloys and micellar systems in soft matter, the viral capsid structures can be of crystalline and quasicrystalline types. We reveal the local quasicrystalline order of proteins in small spherical viral capsids using their nets of dodecahedral type. We show that the structure of some of the viral shells is well described in terms of a chiral pentagonal tiling, whose nodes coincide with centers of mass of protein molecules. The chiral protein packing found in these capsids originates from the pentagonal Penrose tiling (PPT), due to a specific phason reconstruction needed to fit the protein order at the adjacent dodecahedron faces. Via examples of small spherical viral shells and geminate capsid of a Maize Streak virus, we discuss the benefits and shortcomings of the usage of a dodecahedral net in comparison to icosahedral one, which is commonly applied for the modeling of viral shells with a crystalline local order.

Isolation, characterization and comparative study of starches from selected Zingiberaceae species, a non-conventional source

• The starch isolates exhibited high enzyme digestibility . • The shape varies from oval to spheroidal forms in the range of 2–30 μm. • XRD patterns revealed the B and C type of crystallinity. • Thermal studies showed greater degree of gelatinization. • IR spectra determined the polysaccharide nature of the starch.

ZnO1-xTex thin films deposited by reactive magnetron co-sputtering: composition, structure and optical properties

ABSTRACTZnO1-xTexthin films were deposited by DC reactive magnetron co-sputtering using pure Zn and Te targets. Te atomic concentration in the films ranged from x=0 to 0.33 by adjusting the applied power on the targets or varying the cathode-substrate distance. Chemical composition and crystalline structure were determined by RBS experiments and X-ray Diffraction, respectively. For low Te atomic concentrations (x≤0.04) the deposited ZnO1-xTexfilms showed a crystalline structure ZnO wurtzite type however, for increasing Te concentration significant broadening and decreasing intensities of the main peaks belonging to pure ZnO films together with some weak peaks characteristic of crystalline Trizinc Tellurate salt have appeared. For the highest x values some non-identified weak peaks beside to some others peaks corresponding to the crystalline phases mentioned above as well as, a broad band probably associated to amorphous TeO2phase were observed. A preliminary optical characterization of the samples point out the possibility of different electronic transitions within the ZnO band gap.

Investigation on the film-coating mechanism of alumina-coated rutile TiO2 and its dispersion stability

The alumina and alumina-coated rutile TiO2 samples were synthesized by the chemical liquid deposition method under various pH values and aging temperature. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ζ-potential as well as X-ray photoelectron spectroscopy (XPS). The relationship between pH values, the dispersion stability, crystalline types and microstructure of alumina-coated rutile TiO2 samples were studied. It is indicated that the coating film exhibited amorphous hydrous alumina (at pH 3–7), boehmite (at pH 7–9) and bayerite (pH > 11), respectively. And the higher aging temperature was in favor of the elevation of boehmite content of coating film. As the boehmite content increased, the dispersion stability was gradually enhanced and the prepared sample exhibited optimum dispersion stability at pH 9 and aging temperature 200°C, respectively. The increase of steric hindrance and electrostatic repulsion led to the promotion of dispersion stability via coating hydrous alumina film on the surface of rutile TiO2. The detection of AlO and the significantly enhancement of AlOTi intensity confirmed that the film coating process should be main attributed to both chemical bonding and physical adsorption.

Carotenoid Profile, Antioxidant Capacity, and Chromoplasts of Pink Guava (Psidium guajava L. Cv. 'Criolla') during Fruit Ripening.

Pigments of pericarp and pulp of pink guava (Psidium guajava L. cv. 'Criolla') were investigated to elucidate the profile and the accumulation of main carotenoids during four stages of fruit ripening by using HPLC-DAD and APCI-MS/MS analysis. Seventeen carotenoids were identified, and changes in their profile during fruit ripening were observed. The carotenoids all-trans-β-carotene, 15-cis-lycopene, and all-trans-lycopene were present in all ripening stages, but all-trans-lycopene was found to be predominant (from 63% to 92% of total carotenoids) and responsible for the high lipophilic antioxidant capacity determined by spectrophotometric assays. By using light and transmission electron microscopy, the development of chromoplasts in pericarp and pulp was demonstrated. The accumulation of all-trans-lycopene and all-trans-β-carotene coincided with the development of large crystals; the chromoplasts of pink guava belong, therefore, to the crystalline type.

Morphological and structural changes of starch during processing by melt blending

The morphological and structural changes of the granule architecture of normal starch during the melt blending in a batch mixer were investigated. Native potato, maize, and chestnut starch with different crystal structures were used as raw materials. Samples obtained at different times of melt blending were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and polarized light (PL) microscopy techniques. The variation of torque versus time depended on the starch type; the thermo-plasticization of potato starch (B-type) occurred in two steps, whereas that of maize (A-type) and chestnut (C-type) starches took place in one step. An enhancement of the thermo-plasticization after 15 min of starch processing was not observed by SEM and PL microscopy. However, the potato starch with longer amylopectin chains and higher phosphorus content presented a higher extent of destructurization when compared with the maize and chestnut starches. The XRD patterns of the plasticized starch samples showed residual and V-type induced crystallinity, corroborating the partial thermo-plasticization of starches. The extent of thermo-plasticization depended on the crystallinity type and phosphorus content of normal starch.

Induction of Somatic Embryogenesis from Cocoa Farmer Field Collection of ICT - Peru

To induce the formation of embryogenic structures from staminodes, in 10 cocoa genotypes (Theobroma cacao L.) from the ICT Collection, the influence of the combination of two growth hormones (2,4 Dichlorophenoxyacetic 2,4 -D and Thidiazuron TDZ) was studied. Floral explants (staminodes), were induced to form calli in a culture medium supplemented with modified DKW mineral salts. At 12 days of implantation in the culture medium, the explants responded to the callus induction with a bulge at the base, covering the explants totally with callus at 40 days of culture. Embryogenic expression was shown at 52 days of culture. The genotypes ICT-2161 and ICT-2142 shows the highest percentage of somatic embryogenesis. Four types of callus, fine crystalline, thick crystalline, semi-compact and compact were observed. In addition, a clear organogenic response was observed when roots were formed from the callus generated.

Growth undercooling in multi-crystalline pure silicon and in silicon containing light impurities (C and O)

Undercooling during the solidification of silicon is an essential parameter that plays a major role in grain nucleation and growth. In this study, the undercooling of the solid-liquid interface during growth of multi-crystalline silicon samples is measured for two types of silicon: pure, and containing light elements (carbon and oxygen) to assess and compare their impact on crystal growth. The solid-liquid interface undercooling is measured using in situ and real time X-ray synchrotron imaging during solidification. As a subsequent step, ex situ Electron Backscattered Diffraction (EBSD) is performed to obtain information about the crystalline structure, the grain orientation and the grain boundary character. Two main conclusions arise: (i) the undercooling of the global solid-liquid front increases linearly with the growth rate which indicates uniform attachment, i.e. all atoms are equivalent, (ii) the same trend is observed for pure silicon and silicon containing carbon and oxygen. Indeed, the growth law obtained is comparable in both cases, which suggests that the solutal effect is negligible as concern the undercooling in the case of a contamination with carbon (C) and oxygen (O). However, there is a clear effect of the impurity presence on the crystalline structure and grain boundary type distribution. Many grains nucleate during growth in samples containing C and O, which suggests the presence of precipitates on which grain nucleation is favored.

Influence of dissolved oxygen on the protectiveness and morphological characteristics of calcareous deposits with galvanostatic polarization

The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied. When the dissolved oxygen concentration was less than 7 mg L−1, the cathodic protection potential showed a plateau at the initial polarization, and then quickly shifted negatively. While the dissolved oxygen was more than 9 mg L−1, the potential shifted negatively in a linear form. After 168 h of polarization, the final protection potential shifted negatively with the decreasing dissolved oxygen concentration. The deposition progress was monitored by electrochemical impedance spectroscopy, and only one single loop was found in Nyquist diagram, indicating deposits of ineffective protectiveness precipitation under the experimental conditions. The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique. The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration, such as 1 mg L−1, resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor. Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions, and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.

Effect of Diazotated Sulphonated Polystyrene Films on the Calcium Oxalate Crystallization

Pathological crystallization of calcium oxalate (CaOx) inside the urinary tract is called calculi or kidney stone (Urolithiasis). CaOx exhibits three crystalline types in nature: CaOx monohydrate COM, dihydrate COD and trihydrate COT. COD and COM are often found in urinary calculi, particularly COM. Langmuir monolayers, membrane vesicles, phospholipids’ micelles, among others, have been adopted as simplified biomimetic template-models to study in vitro the urolithiasis through CaOx. The nucleation and crystal growth of COM on self-assembled lipid monolayers have revealed that the negatively charged phosphatidylserine interface is a strong promoter of COM. Herein, we describe the synthesis and physicochemical characterization of diazotated sulphonated polystyrene films (DSPFs), prepared from various aminocompounds varying their polarity degree i.e., polar, non-polar and acidic DSPF derivatives. We also used these DSPFs as polymeric templates in crystallization experiments of CaOx in vitro. Images obtained by optical microscopy and scanning electron microscopy confirmed the precipitation of COM crystals on the DSPF surface. The employment of functionalized polymeric films as templates for CaOx crystallization represents a viable approach for understanding inorganic mineralization.

Effect of sputtering power on crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO transparent conducting thin films for optoelectronic devices

The crystallinity and intrinsic defects of transparent conducting oxide (TCO) films have a high impact on their optical and electrical properties and therefore on the performance of devices incorporating such films, including flat panel displays, electro-optical devices, and solar cells. The optical and electrical properties of TCO films can be modified by tailoring their deposition parameters, which makes proper understanding of these parameters crucial. Magnetron sputtering is the most adaptable method for preparing TCO films used in industrial applications. In this study, we investigate the direct and inter-property correlation effects of sputtering power (PW) on the crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO (AZO) TCO films. All of the films were preferentially c-axis-oriented with a wurtzite structure and had an average transmittance of over 80% in the visible wavelength region. Scanning electron microscopy images revealed significantly increased AZO film grain sizes for PW ≥ 150 W, which may lead to increased conductivity, carrier concentration, and optical band gaps but decreased carrier mobility and in-plane compressive stress in AZO films. Photoluminescence results showed that, with increasing PW, the near band edge emission gradually dominates the defect-related emissions in which zinc interstitial (Zni), oxygen vacancy (VO), and oxygen interstitial (Oi) are possibly responsible for emissions at 3.08, 2.8, and 2.0 eV, respectively. The presence of Zni- and Oi-related emissions at PW ≥ 150 W indicates a slight increase in the presence of Al atoms substituted at Zn sites (AlZn). The presence of Oi at PW ≥ 150 W was also confirmed by X-ray photoelectron spectroscopy results. These results clearly show that the crystallinity and intrinsic-defect type of AZO films, which dominate their optical and electrical properties, may be controlled by PW. This understanding may facilitate the development of TCO-based optoelectronic devices for industrial production.

A facile synthesis of UiO-66 systems and their hydrothermal stability

Zirconium-based UiO-66 type MOFs were synthesized using a standard reflux apparatus under a nitrogen atmosphere. This simple synthetic protocol was scaled up to 1 L scale, and can be readily scaled up to allow industrial production of high quality, homogeneous crystalline UiO-66 type MOF materials. The MOFs synthesized in this work exhibited excellent hydrothermal stability.

Luminescence of Donor-acceptor-pair in Fluorescent 4H-SiC Doped with Nitrogen, Boron and Aluminum

Fluorescent 4H-SiC, co-doped with donor and acceptor impurities, can work as phosphor for visible light emission by recombination. Donor concentration and acceptor impurities are two important factors which influence luminescent properties of fluorescent 4H-SiC. In this study, 3 inch N-B-Al co-doped 4H-SiC crystals were prepared by physical vapor transport method. Crystalline type and N-B-Al concentration of the doped 4H-SiC were measured by Raman spectrum and secondary ion mass spectra. Influences of doping concentrations on the photoluminescence were studied by photoluminescence excitation and emission spectra, luminescence decay curves, and internal and external quantum efficiencies. It is found that p-type fluorescent 4H-SiC with low Al doping concentration shows intensive yellow-green fluorescence at room temperature. Heavily doped N and B and lightly doped Al in 4H-SiC produce enough electron hole pairs for the recombination. This sufficient recombination enhances internal quantum efficiency of fluorescent 4H-SiC. Furthermore, the recombination is also helpful to increase their photoluminescence intensity and average fluorescence lifetime.

CuZrO3nanoparticles catalyst in aerobic oxidation of vanillyl alcohol

A highly crystalline, mesoporous and perovskite type CuZrO3nanoparticles catalyst was preparedviaa simple and facile one pot solvent evaporation method.

Green synthesis and characterisation of L-Serine capped magnetite nanoparticles for removal of Rhodamine B from contaminated water

ABSTRACTThis paper describes a green one-pot synthesis of L-Serine (L-Ser) capped magnetite nanoparticles (Fe3O4 NPs) and its potential application for adsorption of RhB dye from aqueous solution. The surface property, structure, morphology and magnetic properties of as prepared L-Ser capped Fe3O4 NPs were characterised through UV-Visible spectroscopy, Fourier transform-infrared spectroscopy, X-Ray Diffraction (XRD), scanning electron microscope, transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The XRD results were indicated the formation of high crystalline spinel type Fe3O4 NPs. TEM images were shown the spherical shape of L-Ser capped Fe3O4 NPs with particle size of 5.9 nm. The VSM curve showed the superparamagnetic behaviour of L-Ser capped Fe3O4. A plausible interaction mechanism of L-Ser and Fe3O4 NPs was also investigated. L-Ser capped Fe3O4 NPs due to its large surface area and a strong magnetism was shown potential adsorption efficiency towards RhB dye from aqueous solution. The adsorption isotherm data fitted well with Langmuir isotherm model and the monolayer adsorption capacity (qe,exp) was found to be 6.82 mg/g at pH 7.4 and 300 K. The experimental kinetic data fitted very well with the pseudo-second-order model. The thermodynamic studies reveal that adsorption efficiency is critically dependent on temperature.

Effects of single and dual heat-moisture treatment combined with sodium alginate on the physicochemical properties of normal cornstarch

Modified starch is considered to be an important ingredient in the application of food industry. The present study investigates the physicochemical properties of normal cornstarch (NCS) treated with a single heat-moisture treatment (SHMT) or a dual heat-moisture treatment (DHMT) with an interval storage temperature of 25 °C (DHMT25), 4 °C (DHMT4) and −20 °C (DHMT-20) in the presence of sodium alginate (AG). The results showed that both SHMT and DHMT combined with AG increased the pasting temperature (PT), gelatinization conclusion temperature (Tc), gelatinization temperature range (Tc–To), and gel hardness of NCS, but they decreased the pasting viscosities, gelatinization onset temperature (To), gelatinization enthalpy (ΔH), and relative crystallinity (RC) of NCS. Neither SHMT nor DHMT combined with AG addition changed the crystalline type of NCS. Sodium alginate–normal cornstarch (AG-NCS) mixtures after SHMT showed the highest PT value and gel hardness, and they showed the lowest breakdown (BD) and setback (SB) values, indicating that AG-starch mixtures with SHMT had superior mechanical and thermal stability. AG-NCS after DHMT-20 showed the highest Tc and Tc–To values as well as the lowest ΔH and RC values, suggesting that the hydrothermal treatment had an effect on the structure changes of starch molecules. Above all, both SHMT and DHMT had effects on the properties of AG-NCS.

Rheology of starch nanoparticles as influenced by particle size, concentration and temperature

Starch nanoparticles (SNP) were isolated from native starches of different botanical origins, showing comparable amylose contents but different crystalline types. The objective was to determine if variations in the morphology and thermal stability of SNP influences the aqueous rheology at room and elevated temperatures. A comparison of the particle size distribution of SNP, both in their dry state and in aqueous suspension at room and elevated temperatures, revealed substantial diversity in the thermal stability of SNP. The SNP from all starch sources were round in shape, but varied in their size distribution. At 5% (w/v) the SNP suspensions formed a thick paste that demonstrated a pseudoplastic behavior. The viscosity and viscoelastic behavior significantly varied among the starch sources as a function of shear, frequency and temperature. A model explaining the viscoelastic behavior of SNP has been proposed, which predicts the composition of both the continuous and dispersed phases. The data suggest that careful selection of processing conditions, such as heating temperature and shearing conditions, is required to achieve the target functionality of SNP in food and industrial applications.