Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution.

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L-1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV-vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

In-Depth Insight into Corrosion Inhibition Performance of Sweet Potato Leaf Extract as a Green and Efficient Inhibitor for 6N01 Al Alloy in the Seawater: Experimental and Theoretical Perspectives.

Corrosion protection of metal has become an important and urgent topic, which requires the development of an inexpensive, environmentally friendly, and highly efficient corrosion inhibitor. Herein, a sweet potato leaf extract (SPL) was obtained by a simple water-based extraction method and then as a green corrosion inhibitor for 6N01 Al alloy in the seawater was well investigated by the weight loss method and various electrochemical tests. Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) spectroscopies were carried out to investigate the compositions of SPL. The findings from the potentiodynamic polarization (PDP) curves suggest that SPL functions as a typical mixed-type corrosion inhibitor. Notably, the maximum corrosion inhibition efficiency reaches 94.6% following a 36 h immersion period at 25 °C. The adsorption behavior of SPL on the Al alloy surface belongs to the Langmuir adsorption isotherm. The Gibbs free energy value illustrates that the adsorption of SPL contains both physisorption and chemisorption. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) indicate that SPL is firmly attached to the Al alloy surface by making a protective layer, which can effectively inhibit the corrosion of the Al alloy in the seawater. Furthermore, quantum chemical calculations were applied to validate the chemical adsorption and elucidate the relationship between the electronic structure of the active components in SPL and their effectiveness in corrosion inhibition.

Structural Features, Physicochemical Properties, and In Vitro Digestibility of the Starch-Lipid Complexes Formed between High Amylose Starch and Stearic Acid or Potassium Stearate.

Starch-lipid complexes were prepared from high amylose starch (HAS) with stearic acid (SA) or potassium stearate (PS) at different molar concentrations. The complexes (HAS-PS) formed between HAS and PS showed polyelectrolyte characteristics with ζ-potential ranging from -22.2 to -32.8 mV, and the electrostatic repulsion between anionic charges restricted the starch chain reassociation and facilitated the formation of V-type crystalline structures upon cooling. The hydrophobic effects enabled recrystallization of the SA, and the HAS-SA complexes exhibited weaker V-type crystalline structures than the HAS-PS complexes; both HAS-SA/PS complexes were of a similar "mass fractal" type, with a dimension varied from 2.15 to 2.96. The HAS-SA complexes had a considerable content of resistant starch (RS, 16.1~29.2%), whereas negligible RS was found in the HAS-PS complexes. The findings from the present study imply that the molecular order of starch chains and the macro-structures of starch particles are more important to regulate the digestibility of starch-lipid complexes than the crystalline structures.

Production and characterization of recrystallized linear α-glucans at different temperatures for controllable thermostability and digestibility.

Molecular structure of linear α-glucans (LAGs) and crystallization temperature have great effects on the thermostability and digestibility of recrystallized LAGs, but the recrystallization behaviors of LAGs in response to temperature remain unclear. Here LAGs with different lengths were prepared from amylopectin via chain elongation and debranching. Recrystallization of LAGs at 4 °C yielded B-type crystalline structure with relative crystallinity ranged from 23.7% to 46.1%. With a chain length of 40.2, an A-type allomorph was observed for a slow recrystallization at 50 °C. Differential scanning calorimetry suggested that A-type crystal had a higher thermostability than the B-type crystal, and increasing LAGs' chain length improved the dimension of double helices, whose assembly produced starch crystallites that enhanced the thermostability and decreased the in vitro digestibility of recrystallized LAGs. An improved thermostability of recrystallized LAGs preserved their ordered structures and kept the resistance to digestive enzymes, with a RS content up to 75.4%.

Molecular modulating of amylopectin's structure promoted the formation of starch-unsaturated fatty acids complexes with controlled digestibility and improved stability to oxidation.

In this study, waxy corn starch (WCS) was modified by amylosucrase and pullulanase, producing linear starch chains with elongated length that favored the complexation with unsaturated fatty acids (uFAs). Compared to native WCS, the amylosucrase-modified WCS with an average chain length of 47.8 was easier to form V-type complexes with oleic acid, while increasing the degree of unsaturation impeded the formation of V-type complexes. The pullulanase treatment hydrolyzed the branching points of amylosucrase-modified WCS and the linear starch chains could forme V-type complexes with oleic acid, linoleic acid, and linolenic acid, with V-type crystallinity decreasing from 38.2 % to 20.1 %. V-type complexes had a lower thermal stability than the B-type starch crystallites, and their peak melting temperature ranged from 67.2 to 79.0 °C. The content of resistant starch in the complexes was in the range of 21.8 %-40.9 % and the formation of V-type complexes decreased the susceptibility of uFAs to oxygen.

Corrosion inhibition activity of a natural polysaccharide from Dysosma versipellis using tailor-made deep eutectic solvents.

In this work, a total of 18 types of choline chloride, betaine, and L-proline-based deep eutectic solvents (DESs) were synthesized to determine the extraction yield of a natural polysaccharide (PSA) from Dysosma versipellis using an ultrasound-assisted extraction method. Results indicate that the choline-oxalic acid-based DES has the best extraction yield for PSA due to the proper physical-chemical properties between PSA and DES. To evaluate the optimal extraction conditions, a response surface methodology was carried out. Under the optimal conditions, the extraction yield of PSA reaches 10.37 % (± 0.03 %), higher than the conventional extraction methods. Findings from FT-IR and NMR suggest that the extracted PSA belongs to a neutral polysaccharide with (1 → 6)-linked α-d-glucopyranose in the main chain. Interestingly, results from various electrochemical measurements show the extracted PSA exhibits excellent corrosion inhibition performance for mild steel (MS) in a 0.5 M HCl solution, with 90.8 % of maximum corrosion inhibition efficiency at 210 mg L-1. SEM and XPS measurements reveal the formation of a protective layer on the MS surface. The adsorption behaviour of extracted PSA well obeys the Langmuir adsorption isotherm containing the chemisorption and physisorption. Additionally, theoretical calculations validate the experimental findings.

Long-Term Retrogradation Properties and In Vitro Digestibility of Waxy Rice Starch Modified with Pectin.

In recent years, the blending of hydrocolloids and natural starch to improve the properties of natural starch has become a research hotspot. In this study, the effects of pectin (PEC) on the retrogradation properties and in vitro digestibility of waxy rice starch (WRS) were investigated. The results showed that PEC could significantly (p < 0.05) reduce the retrogradation enthalpy and reduce the hardness of WRS gel. X-ray diffraction results indicated that PEC could reduce the relative crystallinity of the composite system, and the higher the PEC content, the lower the relative crystallinity. When the PEC content was 10%, the relative crystallinity of the composite system was only 10.6% after 21 d of cold storage. Fourier transform infrared spectroscopy results proved that the interaction between PEC and WRS was mainly a hydrogen bond interaction. Furthermore, after 21 d of cold storage, the T23 free water signal appeared in the natural WRS paste, while only a small free water signal appeared in the compound system with 2% PEC addition. Moreover, addition of PEC could reduce the starch digestion rate and digestibility. When the content of PEC increased from 0% to 10%, the digestibility decreased from 82.31% to 71.84%. This study provides a theoretical basis for the further application of hydrocolloids in starch-based foods.

Physicochemical Properties of the Rice Flour and Structural Features of the Isolated Starches from Saline-Tolerant Rice Grown at Different Levels of Soil Salinity.

Three varieties of saline-tolerant indica rice were grown in soils with salinities of 0.0-0.6% (w/w). The rice grown at salinities of 0.3 and 0.6% had a smaller grain dimension than its counterpart. Salinity stress altered the physiology of plants, leading to changes in the basic chemical compositions for all rice varieties, e.g., increasing the soil salinity improved the content of rice protein (RP). The pasting and rheological properties of the rice flour highly depended on its chemical compositions. An increase of RP inhibited the swelling of starch granules and accordingly decreased the peak viscosity of rice flour, while the aggregation of RP weakened the gel structure of the cooked rice flour. The isolated starches showed polyhedral granules, and they all had an A-type crystalline structure with relative crystallinity varying from 34.16 to 45.40%. Moreover, increasing the soil salinity enhanced the lamellar order and periodic length of the isolated starches.

Natural chitosan-based carbon dots as an eco-friendly and effective corrosion inhibitor for mild steel in HCl solution.

Polysaccharide chitosan and L-histidine were applied to synthesize chitosan-based carbon dots (CA-CDs) by a simple laser ablation method. After characterization of the CA-CDs by FT-IR, UV-vis, Raman, XRD, TEM, and XPS, the CA-CDs were introduced as an eco-friendly and high-performance corrosion inhibitor for mild steel (MS) in 1.0 M HCl solution. The inhibition action and mechanism of CA-CDs were determined by weight loss and electrochemical measurements, in combination with SEM, AFM, and XPS. The results show that CA-CDs as mixed-type inhibitors could effectively weaken the corrosion of MS in 1.0 M HCl solution, and their maximum inhibition efficiency reaches 97.4 % at 40 mg L-1. The adsorption behavior of CA-CDs well obeys the Langmuir adsorption isotherm containing both chemisorption and physisorption. The chemisorption mainly results from the multiple adsorption sites in the CA-CDs, and the physical adsorption is due to the blocking and barrier effect of CA-CD nanoparticles. Both adsorption behaviors were proposed to elucidate the corrosion inhibition mechanism of CA-CDs.

Impact of crystalline structure on the digestibility of amylopectin-based starch-lipid complexes.

In this study, chain-elongated waxy corn starch (mWCS) was complexed with lauric acid (LA) to produce starch-lipid complexes (mWCS@LA) with a mixture of B- and V-type crystalline structures. Results from in vitro digestion showed that mWCS@LA had higher digestibility than mWCS, and the logarithm of slope plots of mWCS@LA revealed a two-stage digestion pattern, with digestion rate of the first stage (k1 = 0.038 min-1) being much higher than that of the following stage (k2 = 0.0116 min-1). The complexation between the long branch chains of mWCS and LA formed amylopectin-based V-type crystallites that were rapidly hydrolyzed during the first stage. The digesta isolated from the second stage of digestion had a B-type crystallinity of 52.6 %, and starch chains with degree of polymerization of 24-28 mainly contributed to the formation of the B-type crystalline structure. The results from the present study reveal that the B-type crystallites were more resistant to amylolytic hydrolysis than the amylopectin-based V-type crystallites.

Dopamine modified natural glucomannan as a highly efficient inhibitor for mild steel: Experimental and theoretical methods.

In this work, Glucomannan was modified with dopamine to synthesize a new polysaccharide Schiff base (GAD). After confirmation of GAD by NMR and FT-IR spectroscopic methods, it was introduced as a sustainable corrosion inhibitor with excellent anti-corrosion action for mild steel in 0.5 M hydrochloric acid (HCl) solution. Employing electrochemical test, morphology measurement, and theoretical analysis, the anticorrosion performance of GAD on mild steel in 0.5 M HCl solution is determined. Maximum efficiency of GAD for suppressing the corrosion rate of mild steel at 0.12 g L-1 reaches 99.0 %. After immersion in HCl solution for 24 h, the results from scanning electron microscopy indicate that GAD is firmly attached to the mild steel surface by making a protective layer. According to the X-ray photoelectron spectroscopy (XPS), FeN bonds existed on the steel surface indicate the presence of chemisorption between GAD and Fe to form stable complexes attracted to the active position on the mild steel. The effects of Schiff base groups on the corrosion inhibition efficiencies were also investigated. Moreover, the inhibition mechanism of GAD was further illustrated by the free Gibbs energy, quantum chemical calculation and molecular dynamics simulation.

Tuning the electrostatic interaction between rice protein and carboxymethyl cellulose toward hydrophilic composites with enhanced functional properties.

Protein-polysaccharide interactions have attracted much attention due to inherent potential in generating new structures and functionalities. In the present study, by simply mixing rice proteins (RPs) with carboxymethyl cellulose (CMC) at pH 12.0 prior neutralization, novel protein-polysaccharide complexes (RCs) were structured with water dispersibility and functionalities highly dependent on the degree of substitution (DS) and molecular weight (Mw) of CMC. Specifically, the water-dispersibility of RPs was increased from 1.7 % to 93.5 % at a RPs/CMC mass ratio of 10:1 with CMC of DS1.2 (Mw = 250 kDa). Fluorescence and circular dichroism spectra showed suppressed folding tendency of RPs by CMC during neutralizing the basicity, indicating controllable protein conformations. Furthermore, the structures of RCs became more unfolded for CMC with a larger DS or a smaller Mw. This enabled RCs with highly controllable functionalities in terms of emulsifying and foaming properties, which may have promising applications in developing food matrix with customized structures and textures.

Resistant starch formation mechanism of amylosucrase-modified starches with crystalline structure enhanced by hydrothermal treatment.

The aim of this study was to reveal the underlying mechanism contributing towards the formation of resistant starch (RS) in amylosucrase-modified starches with crystalline structure enhanced by hydrothermal treatment. The branch chains of waxy corn starch were continuously elongated by amylosucrase, and the retrogradation of elongated starches with weight-average chain length (CLw¯) of 27.0-37.6 yielded B-type retrograded starches (MSs) with crystallinity increasing from 33.1 % (MS-5) to 41.4 % (MS-30). Increasing the starch crystallinity improved the content of RS from 6.7 % of MS-5 to be as much as 41.0 % of MS-30. During the hydrothermal treatment, MS-5 with CLw¯ of 27.0 favored the B â†’ A allomorphic transition, leading to the decreased starch digestibility. Moreover, the hydrothermal treatment facilitated the assembly of double helices to increase starch crystallinity, which further increased the content of RS. The findings of the present study may assist the preparation of functional starches with controllable digestibility.

Simultaneous Rapid Determination of Seven Alternaria Toxins in Tuberous Crops during Storage Using QuEChERS Coupled with Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry.

Robust and sensitive ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied for the detection of seven Alternaria toxins (ATs) in tuberous crops. The influence of tuber conditions (fresh, germinated, and moldy) during storage on the concentration of the seven ATs is also investigated. ATs were extracted with acetonitrile under acidic conditions and purified with a C18 adsorbent. ATs were scanned with electrospray ionization (positive/negative ion) dynamic switching and detected in MRM mode. Calibration curve analysis results reveal good linear relationships in all toxin concentration ranges (R2 > 0.99). The limit of detection and limit of quantification were 0.25-0.70 and 0.83-2.31 µg/kg, respectively. The average recoveries of the seven ATs were 83.2-104% with intra-/inter-day precision at 3.52-6.55% and 4.02-7.26%, respectively. The developed method provided adequate selectivity, sensitivity, and precision in detecting the seven ATs at trace levels, and dispensed with standard addition or matrix-matched calibration to compensate for matrix effects. ATs in the fresh, germinated, and moldy samples of tuberous crops in storage (taro, potato, sweet potato, yam, cassava) were analyzed with this method, and the concentrations were 2.01-14.51 µg/kg and significantly increased with storage duration. ALS was detected in most samples, whereas no quantities of ALT and ATX-I were detected. AME was often detected in combination with AOH in sweet potatoes. TeA and Ten were mostly detected in taro, potato, and yam. The established method could be used for the simultaneous detection and quantification of multicomponent toxins in elaborate matrices.

Fabrication and characterization of starch-lipid complexes using chain-elongated waxy corn starches as substrates.

In this study, waxy corn starch (WCS) was enzymatically modified by amylosucrase, followed by complexation with lauric acid (LA) to produce starch-lipid complexes. Compared to the native WCS with average chain length (CL¯) of 25.4, the amylosucrease-modified WCSs showed a significantly higher CL¯ ranging from 29.3 to 52.5. The complexation with lauric acid inhibited the reassociation of starch chains, producing V-type complexes with crystallinity reached as much as 42.4 %. Besides, the melting of V-type complexes presented endothermic peaks at Tp of 55.1-60.4 °C, and thermal stability of V-type complexes had a negative correlation with the V-type crystallinity. In vitro digestion implies that the formation of V-type complexes gradually increased the content of rapidly digestible starch and accordingly decreased the content of resistant starch. This study may provide an efficient technology to produce V-type starch-lipid complexes with controllable physical and digestion properties using waxy starch as substrate.

Engineering the Structural Defects of Spinel Oxide Nanoneedles by Doping of V for a Highly Efficient Oxygen Evolution Reaction.

Rational design of multi-structural defects in the transition-metal oxides is a very alluring and challenging strategy to significantly improve its oxygen evolution reaction (OER) performance. Herein, a simple and promising element doping approach is demonstrated to fabricate a poor-crystalline V-doping CuCo2O4 (V-CuCo2O4) nanoneedle with rich oxygen vacancies (Vo), partially amorphous phase, and Co2+ defects on the carbon fiber (CF) (V-CuCo2O4/CF). The results indicate that the V doping could further weaken the crystallinity of V-CuCo2O4, providing the thoroughfares for the convenience of electrolyte penetration and the exposure of active sites. Meanwhile, [CoO6] octahedron in the V-CuCo2O4 lattice is gravely distorted due to a strong electronic interaction between the doped V and Co atoms, creating more Co2+ active species. With the merits of these multiple structural defects, V-CuCo2O4/CF exhibits rich active sites, and its intrinsically electrocatalytic activity is significantly enhanced. The optimized V-CuCo2O4/CF electrocatalyst has a significantly enhanced OER activity with a required low overpotential of ∼204 and ∼246 mV at a current density of 100 and 300 mA cm-2, respectively, a small Tafel slope of 40.7 mV dec-1, and excellent stability in an alkaline medium. Furthermore, the results from the projected partial density of states calculation not only demonstrate that the 3-fol-coordinated Co near Vo bonded with Cu and V sites (Cu-Co(surf-Vo)-V) exhibits an enhanced electronic transfer activity but also reveal that the doped V could protect the Co sites from the deactivation by intermediates overbinding on the V sites. This work provides new insights into structure engineering of spinel phase copper cobaltite, resulting in significantly boosting electrocatalytic OER activity.

Validation of the Asia-Pacific colorectal screening score and its modified versions in predicting colorectal advanced neoplasia in Chinese population.

BACKGROUND: Colorectal cancer is one of the most common cancers in the world. Several studies suggest using the Asia-Pacific colorectal screening (APCS) score and its modified versions to select high-risk populations for early colonoscopy, but external validation remains rare, and which score should be selected for CRC screening in China is unclear. Validation of multiple scores in the same population might help to choose the best performing score. METHODS: We conducted a cross-sectional study under the framework of Cancer Screening Program in Urban China, data from asymptomatic colorectal cancer screening in Xuzhou was used to validate the APCS score, the colorectal neoplasia predict (CNP) score, the Korean colorectal screening (KCS) score, the Modified APCS score and the 8-point risk score in predicting colorectal advanced neoplasia (CAN). RESULTS: 1804 subjects were included in the analysis and 112 CAN (6.21%) was detected. In each score, the detection rate of CAN was higher in the high-risk group than in the non-high-risk group (P < 0.05), and the RR (95%C.I.) ranged 2.20 (1.50-3.22) [8-point risk] to 4.00 (2.41-6.65) [Modified APCS]. The c-statistics (95%C.I.) of the scoring systems ranged from 0.58 (0.53-0.62) [8-point risk] to 0.65 (0.61-0.69) [KCS]. The sensitivity (95%C.I.) of these systems ranged from 31.25 (22.83-40.70) [8-point risk] to 84.82 (76.81-90.90) [Modified APCS], while the specificity (95%C.I.) ranged from 43.50 (41.12-45.90) [Modified APCS] to 83.81 (81.96-85.53) [8-point risk]. Using the APCS scoring system as a comparator, the net reclassification improvement (NRI) of each modified version ranged from - 10.34% (95%C.I.: - 22.63 to 1.95%) [8-point risk] to 4.79% (95%C.I.: - 1.50% to 11.08) [KCS]. The colonoscopy resource load (95%C.I.) ranged from 9 [1-3] [8-point risk] to 11 [3-5] [APCS and Modified APCS]. CONCLUSIONS: The APCS score and its modified versions have certain ability to predict the risk of advanced neoplasia and reduce the resource load. The modified APCS score and the KCS score seemed the preferable systems to classify high risk subjects based on its high RR, sensitivity and predictive ability in the selected population. Future research could focus on adding risk factors or combining with laboratory test results to improve the predictive power of the scoring system.

Metal organic frameworks (MOFs) as multifunctional nanoplatform for anticorrosion surfaces and coatings.

Corrosion of metallic materials is a long-standing problem in many engineering fields. Various organic coatings have been widely applied in anticorrosion of metallic materials over the past decades. However, the protective performance of many organic coatings is limited due to the undesirable local failure of the coatings caused by micro-pores and cracks in the coating matrix. Recently, metal organic frameworks (MOFs)-based surfaces and coatings (MOFBSCs) have exhibited great potential in constructing protective materials on metallic substrates with efficient and durable anticorrosion performance. The tailorable porous structure, flexible composition, numerous active sites, and controllable release properties of MOFs make them an ideal platform for developing various protective functionalities, such as self-healing property, superhydrophobicity, and physical barrier against corrosion media. MOFs-based anticorrosion surfaces and coatings can be divided into two categories: the composite surfaces/coatings using MOFs-based passive/active nanofillers and the surfaces/coatings using MOFs as functional substrate support. In this work, the state-of-the-art fabrication strategies of the MOFBSCs are systematically reviewed. The anticorrosion mechanisms of MOFBSCs and functions of the MOFs in the coating matrix are discussed accordingly. Additionally, we highlight both traditional and emerging electrochemical techniques for probing protective performances and mechanisms of MOFBSCs. The remaining challenging issues and perspectives are also discussed.

Removal of aflatoxin B1 from aqueous solution using amino-grafted magnetic mesoporous silica prepared from rice husk.

It is urgent to solve the contamination of aflatoxin B1 (AFB1) in food and water. In this study, the mesoporous silica was prepared from rice husk, which was then magnetized using the precipitation technique, followed by amino-modification with 3-aminopropyltriethoxysilane, forming amino-grafted magnetic mesoporous silica (NMMS). X-ray diffraction, Fourier transformed infrared spectra, and thermogravimetric analysis showed the successful grafting of amino groups on NMMS with a percentage of grafting up to 13.33%. The NMMS had an adsorption capacity of 169.88 µg/g and a removal rate of 93.43% for AFB1 in aqueous solutions at 20 °C, pH 7.0 for 2.0 h. The adsorption of AFB1 by NMMS followed a quasi-second-order kinetics and fitted well with the Langmuir model. Furthermore, the removal rate of AFB1 by NMMS remained 72.43% after repeating the adsorption-desorption process for five times. This study provided a facile approach to prepare NMMS for effective removal of AFB1.