Search

Highlights • Two processes are used to prepare dialdehyde starch nanoparticles. • Starch nanocrystals showed great stability and dispersibility after oxidation. • The crystallinity and particle size of dialdehyde starch nanoparticles are different. • Starch nanocrystals have great emulsification properties. Abstract Physicochemical and emulsification properties of dialdehyde starch nanocrystals (DASNCs) and dialdehyde starch nanoparticles (DASNPs) were measured in this study. The starch nanocrystals (SNCs), which are prepared by sulfuric acid hydrolysis, were oxidized by sodium periodate to obtain the DASNCs. The DASNPs were prepared by gelatinization and alcohol precipitation of dialdehyde starch. After oxidization by sodium periodate, the SNCs and SNPs became smaller and more suitable for dispersion. X-ray diffraction results showed that the crystal pattern of the SNCs was preserved after oxidation. However, only a single broad peak at the Bragg angle of the DASNPs was observed. The SNCs and DASNCs can form Pickering emulsions, but the emulsions stabilized by the SNPs and DASNPs could be easily broken. The preparation methods for the two kinds of dialdehyde starch nanoparticles are different, so their structures, properties and applications are different. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Waxy potato starch nanocrystals (SNCs) were modified by octenyl succinic acid. • Crystalline structure of SNCs preserved after the esterification. • Hydrophobicity of SNCs was controlled by adjusting octenyl succinic acid content. • Prominent compatibility and stability of SNCs in chloroform were exhibited. Abstract Waxy potato starch nanocrystals (SNCs) were successfully modified through esterification by using octenyl succinic anhydride (OSA) aiming to improve its hydrophobicity. The SNCs were characterized by using 1H nuclear magnetic resonance (1H NMR) spectroscopy, X-ray diffraction (XRD), Fourier transformation infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), dispersion experiments and scanning electron microscopy (SEM). The degree of substitution (DS) was determined by means of 1H NMR revealed the upward trend with the increase of OSA dosage. XRD displayed the un-changed crystalline structure of SNCs but relative slight decrease of crystallinity. FT-IR spectroscopy showed characteristic absorption of the ester carbonyl groups and carboxylate RCOO− enclosed to 1732 cm-1, 1572 cm-1 respectively in OSA-SNCs. XPS confirmed the introduction of long chain hydrocarbon. The hydrophobicity of the modified SNCs increased with the increase of applied OSA contents. Dispersion experiments revealed the prominent compatibility and stability of nanocrystals in chloroform and acetone. SEM micrographs showed the serious aggregation of OSA-SNCs composed of smaller blocklets with 200–800 nm in size. [ABSTRACT FROM AUTHOR]

A comparative experiment about the production of starch nanocrystals (SNCs) with/without glucoamylase enzymatic pretreatment by sulfate acid hydrolysis from waxy potato starch (WPS) was employed in the present study. The research focused on the enhancement of the preparation efficiency while improving the dispersion of SNCs at the same time. The enzymatic pretreatment resulted in the decrease of acid hydrolysis duration. The minimum size and best dispersibility of nanocrystals was obtained after 5 days of hydrolysis. X-ray diffraction confirmed the increase of crystallinity (from 33% to 50.8%) and the polymorphic transitions (B–A) for nanocrystals harvested at day 5. The structure of nanocrystals was characterized by FT-IR, which suggested the presence of sulfate ester on the surface of SNCs. Zeta potential and size distribution revealed the prominent stability and dispersibility of nanocrystals at pH 7.0. SEM and TEM revealed that SNCs had square shapes with particle sizes ranging from 50 to 100 nm. [ABSTRACT FROM AUTHOR]

The nanocrystalline Fe0.13(CoxNi100−x)0.87 (x = 30, 50, and 80) alloy fiber 50 wt%–epoxy resin composites were prepared by mixing epoxy resin with the alloy fibers. The electromagnetic parameters of the composites were measured using the coaxial line method and the reflection loss was calculated at a frequency range 1–18 GHz. The results show that the nanocrystalline Fe0.13(CoxNi100−x)0.87 alloy fiber–epoxy resin composites have effective microwave absorption characteristics in radar band, which are mainly influenced by the nanocrystalline alloy composition and the composite thickness. This microwave absorption effect largely arises from the eddy current, ferromagnetic resonance, and dielectric loss in the composite. [ABSTRACT FROM AUTHOR]

The article examines how starch nanocrystal-graft-polycaprolactone affects the mechanical properties of waterborne polyurethane (WPU)-based nanocomposites. Grafting with polycaprolactone (PCL) functionalized the surface of starch nanocrystals (StN). It was shown that a loading-level of 5 wt % StN-g-PCL led to a simultaneous improvement of tensile strength and elongation at break, both of which were higher than those of neat WPU.

This article discusses a study which examined the morphology, thermal behavior, mechanical properties and water sensitivity of nanocomposite films prepared from a mixed suspension of hemp cellulose nanocrystals (HCNs) and thermoplastic starch. The study applied several techniques such as scanning electron microscopy, wide-angle X-ray diffraction and tensile testing in the examination. It showed increases in the tensile strength and Young's modulus of the films.

Abstract: Pea starch nanocrystals (PSN) dispersion containing nanocrystals in a range of 30–80nm was prepared from native pea starch (NPS) granules by acid hydrolysis. Two series of films were prepared by blending poly(vinyl alcohol) (PVA) with NPS and PSN, respectively. The effects of NPS and PSN on the structure and properties of the resulting films were comparatively investigated by FTIR, XRD, SEM, and testing of light transmittance, tensile, and moisture uptake. The light transmittance (Tr), tensile strength (σ b), and elongation at break (ε b) of the PVA/NPS films were lower than that of PVA film and decreased with an increase in NPS content. However, the PVA/PSN nanocomposite films containing 5 and 10wt% of PSN content exhibited improved physical properties over the PVA film. The PVA/PSN films showed higher Tr, σ b, and ε b, and lower moisture uptake (Mu) than the corresponding PVA/NPS films with the same component ration. For example, the values of Tr, σ b, ε b, and Mu of the PVA/PSN film containing 10wt% of PSN content were 91%, 40MPa, 734% and 71%, respectively; while those of the corresponding PVA/NPS film were 69%, 35MPa, 579% and 73%, respectively. The results revealed that PSN, comparing with NPS, had much smaller sizes and dispersed more homogeneously in PVA matrix, resulting in stronger interactions with PVA. New applications of native pea starch and its nanocrystals as low-cost fillers were explored in this work, and PSN exhibited greater potential than NPS to improve the properties of PVA-based composites. [Copyright &y& Elsevier]

A self-powered photoelectrochemical (PEC) aptamer probe is presented for the determination of oxytetracycline (OTC). The assay is based on the use of g-C3N4 and NiO nanocrystals (NCs) which form a heterojunction. The latter was prepared by two-step hydrothermal pyrolysis by using the ionic liquid 1-hydroxyethyl-3-methylimidazole chloride which functions as a morphological template to form NiO NCs. The heterojunction exhibits much better electronic conductivity, wider absorption range, higher electron-hole-separation productivity, and stronger photocurrent compared to plain g-C3N4. The heterojunction was adopted to construct a self-powered PEC aptamer probe for OTC detection. An OTC-binding aptamer was immobilized on the heterojunction and the probe was constructed. The aptamer on the probe binding with OTC can form steric hindrance for transmitting of electrons and cause the PEC signal change depending on the OTC concentration. The photocurrent decreases with increasing OTC concentration in the 0.01 to 100 nM concentration range and its detection limit is 4 pM (at S/N = 3). [ABSTRACT FROM AUTHOR]

The influence of excessive lithium on the crystal structure, morphology, and electrochemical properties of Fe-deficient Li x FePO 4 ( x = 1.00, 1.02, 1.04, 1.05) cathode material was investigated using co-precipitation and the carbon thermal method. The X-ray diffraction pattern and Rietveld refinement results show that excessive Li + combines with the phosphate group to form Li 3 PO 4 rather than occupying the Fe site to form antisite pairs. Benefitting from the intrinsic ion conductivity of lithium phosphate, the lithium diffusion coefficient of Li x FePO 4 increases. However, the charge transfer impedance (Rct) also increases with increasing Li content due to the presence of Li 3 PO 4 , a nonconductive phase that can block the electric transfer channel. The biphasic Li x FePO 4 ( x = 1.02) compound shows the best performance. This work suggests an effective and easy way to improve the electrochemical performance by adding excessive Li, which leads to the formation of Li 3 PO 4 . [ABSTRACT FROM AUTHOR]

Abstract Extensive efforts have been devoted to carbon coated LiFePO 4 to optimize its performance by increase conductivity, however, the coating effect on crystalline size and shape have never been touched. Herein, we reveal the influence of carbon content on the crystal orientation, particle size, and electrochemical performance of the nanocrystalline LiFePO 4 , which is synthesized by a hydrothermal method with predominantly (010) faces exposure. We found that an increase of the carbon content from 1.65 to 6 wt% modified the preferential orientation of the LiFePO 4 crystal from the (010) plane to the (100) plane. The solid electrolyte interface resistance R sf also increased, causing a decrease in the electrochemical performance of LiFePO 4 /C cathode materials. Among all the carbon coated samples, LiFePO 4 /C composites coated with 1.65 wt% carbon exhibited the best initial discharge capacity and efficiency of 162 mAh g−1 and 95.4% at 0.1C, respectively. This performance can be attributed to the low R sf value and preferential orientation of the (010) plane. Highlights • The effect of carbon coating on the crystalline orientation and electrochemical performance of LiFePO 4 was investigated. • Preferential orientation transformed from (010) to (100) with increase carbon content. • R sf reached the minimum at 1.65 wt% carbon content and increased with increase carbon content. • LiFePO 4 /C with 1.65 wt% carbon has the best performance because of preferential orientation of (010) plane and low R sf. [ABSTRACT FROM AUTHOR]

In this work, waxy maize starch nanocrystals were prepared by mixed acid of sulfuric acid and hydrochloric acid for the first time. Physicochemical properties, crystalline structure, and particle size of starch nanocrystals prepared by mixed acid (HSNC) were measured. The results showed that there was no difference in particle morphology, group structure, and surface elements of HSNC and starch nanocrystals prepared by sulfuric acid (SNC), which was a conventional preparation method. The yield of HSNC was lower than that of SNC. However, the preparation time of HSNC was greatly shortened to 1 h which is only 0.83 % of the time (5 d) to prepare SNC by the sulfuric acid, and HSNC showed higher relative crystallinity and smaller size than those of SNC. In addition, when the ratio of sulfuric acid and hydrochloric acid to provide H ion concentration was 1:1 to hydrolyze starch for >1 h, the crystal pattern of HSNC would be changed to V-typed, while the crystal pattern of SNC was still A-typed. Thus, this work provided efficient method for preparing starch nanocrystals is provided, which can replace sulfuric acid hydrolysis to prepare SNC. • Mixed acid were used to prepare starch nanocrystals (HSNC) in 1 h • Starch nanocrystals prepared by mixed acid shortened than conventional preparation • HSNC prepared by mixed acid had higher relative crystallinity and smaller size • The crystal pattern of HSNC prepared >1 h would change to V-typed [ABSTRACT FROM AUTHOR]