Inhibitory Activity Properties Research Articles

Enzyme activity inhibition properties of new cellulose nanocrystals from Citrus medica L. pericarp: A perspective of cholesterol lowering.

As a waste material, the amazing potential of cellulose nanocrystals (CNCs) isolated from Citrus medica L. pericarp in being a natural resource of lingo-cellulosic products has never been investigated before. In the present study, an alkaline pretreatment and a two-step bleaching procedure were applied to conduct the desired acid hydrolysis by the usage of 64% sulfuric acid at 50°C for 105 min. The extracted CNCs were distinguished through the means of transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta potential, and energy-dispersive X-ray spectroscopy (EDX). The elimination of peaks, which were accountable for the inducement of hemicelluloses and lignin, was confirmed by the FTIR results and were also validated by the outcomes of XRD that proved the gentle removal of non-cellulosic components. The morphology and size of CNCs were indicated through the FESEM and TEM results. In addition, the spherical forms of synthesized CNCs were observed with a diameter of 46 nm throughout the FESEM images, while displaying a value of 42.54nm as well due to TEM micrographs. The obtained zeta potential displayed a reasonable negative surface charge for CNCs. Furthermore, the cytotoxicity assessment of this product on fibroblast cells was performed to study their susceptibility for bio-medical and cosmetic industrial applications, which resulted in the lack of exhibiting any cytotoxic effects. In conformity to the outcomes of TEM and FESEM, the results of AFM revealed a fine dispersion and spherical form of cellulose nanoparticles. The interaction between HMG-CoA reductase and CNC was studied by the usage of multi-spectroscopic methods and enzyme kinetics to explore the binding mechanism of HMG-CoA reductase-CNC system. Reduced catalytic activity of the occurrence of changes in the secondary structure of HMG-CoA reductase was as a result of interacting with CNC causing a reduction in its catalytic activity.

Synthesis of graphene oxide functionalized by polyaniline coated alpha-zirconium phosphate to enhance corrosion resistance of waterborne epoxy coating

Graphene oxide (GO), a preeminent two-dimensional (2D) material, has great potential application for corrosion protection owing to its excellent barrier properties to gas and liquid. Unfortunately, the poor dispersion in waterborne epoxy resins and excessive surface defects limit the further application of GO. In this study, a novel GO-based nanofiller PZ-GO (GO modified by polyaniline-wrapped alpha-zirconium phosphate) was designed to endow waterborne epoxy coating (WEC) system with durable anti-corrosion performance. Among them, the modification of alpha-zirconium phosphate (α-ZrP) wrapped with polyaniline (PZ) for GO not only enhanced the dispersion of GO but also strengthened its barrier effect. Notably, as a linker between GO and α-ZrP, PANI could also endow the coating with active inhibition performance. Differential scanning calorimetry (DSC) was introduced to investigate the effect of adding nanofillers on ‘Cure Index’ of composites. The ‘Cure Index’ of epoxy resins doped with PZ-GO was 1.139, which was considered as ‘Excellent’ according to the evaluation criteria, proving that the addition of PZ-GO significantly reinforced the curing degree of epoxy resins. A more complete cure of the epoxy resins could provide a stronger barrier ability for the coatings, thus improving the corrosion resistance of the coatings. Furthermore, the anticorrosive behavior of PZ-GO/WEC was analyzed via electrochemical impedance spectroscopy (EIS) and salt spray tests. The results showed that PZ-GO/WEC exhibited great anticorrosive performance (the impedance value was maintained at 8.72 ×10 7 Ω.cm 2 after immersion in 3.5 wt% NaCl solution for 80 days). In particular, PZ-GO/WEC also demonstrated great active inhibition performance. In addition, the active inhibition mechanism of PZ-GO/WEC was revealed by X-ray photoelectron spectroscopy (XPS) analysis of the corrosion products. All results proved that the excellent corrosion protection properties of PZ-GO/WEC for carbon steels originated from the outstanding barrier ability of PZ-GO/WEC and the active inhibition of PANI. In this study, graphene oxide-based nano-fillers for anticorrosive reinforcement of waterborne epoxy coating were prepared by a facile process. In details, α-zirconium phosphate nanosheets with the size of 0.5μ to 1μ was fabricated by a simple hydrothermal reaction. Then, wrapping polyaniline on the surface of α-zirconium phosphate was achieved through in-situ polymerization. Further, graphene oxide was modified with smaller laminar polyaniline-coated alpha-zirconium phosphate via π-π interaction through facile ultrasonic vibration process. • A novel GO-based nanofiller PZ-GO with high barrier abilities and active inhibition properties. • PZ-GO endows waterborne epoxy coating with durable anti-corrosive performance. • PZ-GO/WEC exhibited great active inhibition performance.

Development of an active/barrier bi-functional anti-corrosion system based on the epoxy nanocomposite loaded with highly-coordinated functionalized zirconium-based nanoporous metal-organic framework (Zr-MOF)

For the first time, the UIO-66, NH2-UIO, and NH2-UIO particles covalently functionalized by Glycidyl Methacrylate (GMA@NH2-UIO), were utilized as the novel functional anti-corrosive fillers. The functionality, high surface area, phase composition, excellent thermal properties as well as chemical stability of the Zr-MOFs were proved by FT-IR, BET, XRD, TGA, and water stability tests, respectively. The smart pH-sensitive controlled-release activity of the corrosion inhibitors (i.e., Zr ions and organic compounds) from the prepared Zr-MOFs was proved by the water stability test of the Zr-MOFs particles in the acidic (pH = 2), neutral (pH = 7.5), and alkaline (pH = 12) solutions containing 3.5 wt% sodium chloride. The active inhibition properties of the Zr-MOFs were obtained in saline solution by two methods of (i) the solution phase and (ii) scratched epoxy coated samples containing Zr-MOFs by Tafel polarization method and EIS analysis. According to the EIS data, the excellent barrier (passive) properties of the composite film filled with GMA@NH2-UIO particles (G-UIN/EP) were proved by the highest impedance level at the lowest f (frequency) (log (|Z|10 mHz = 9.86 Ω.cm2), the lowest value of the breakpoint frequency (log (fb) = −1.42 Hz) and the highest coating undamaged index (85.93%) after 120 h of immersion. The salt spray (accelerated corrosion test) test (SST), pull-off (testing the strength of adhesion), and cathodic disbonding test (CDT) experiments showed excellent interfacial-adhesion properties of the G-UIN/EP sample in two dry (unexposed) and wet conditions. The hardness test showed that through the incorporation of the UIO, UIN, and G-UIN particles into the epoxy coating, the hardness, and scratch-resistance of the coating were notably improved.

Development of metal-organic framework (MOF) decorated graphene oxide nanoplatforms for anti-corrosion epoxy coatings

In this study, a novel corrosion protective coating with an excellent barrier, and superior active anti-corrosion characteristics was constructed through a one-pot synthesis method of zeolitic imidazolate framework-8 (ZIF-8) on the graphene oxide sheets. Experimental results proved the successfully synthesize of GO@ZIF-8 particles with a 79% improvement of the specific surface area compared with the neat GO. A corrosion inhibition efficiency of about 79% was recorded for the steel sample immersed in the NaCl solution containing GO@ZIF-8 particles extract by the polarization test, proving the active inhibition properties of GO@ZIF-8 particles. The low-frequency impedance (|Z|10 mHz) values greater than 1010 Ω cm2 were recorded by EIS analysis for the GO@ZIF-8/epoxy coating at all immersion times, indicating the superior barrier anti-corrosion properties of this coating. The pull-off and cathodic delamination tests revealed about 73% and 60% improvements of the epoxy coating cathodic delamination resistance and wet adhesion strength, respectively, in the presence of GO@ZIF-8 particles in comparison with the neat epoxy sample. The EIS outcome revealed a 70% improvement in the corrosion resistance of the GO@ZIF-8 loaded epoxy composites with an artificial defect after 72 h immersion than the neat epoxy sample, indicating the good smart inhibition activity for this sample.

Application of layer-by-layer assembled graphene oxide nanosheets/polyaniline/zinc cations for construction of an effective epoxy coating anti-corrosion system

By a layer by layer deposition approach the grafted graphene oxide (GO) particles were grafted by zinc doped polyaniline (PAni) and then distributed in the epoxy matrix to provide active inhibition/barrier properties simultaneously. The modified/unmodified nanosheets were examined by X-ray diffraction (XRD) analysis and Raman spectroscopy. The corrosion prevention effect of GO-PAni-Zn/epoxy composite was studied by EIS and salt spray test. Results revealed that the GO nanosheets dispersion quality and interfacial interactions were improved after applying PAni-Zn layer, leading to significant improvement in the epoxy coating barrier properties against diffusion of sodium chloride solution. In addition, according to EIS test results the active inhibition properties of the epoxy film was promoted after addition of zinc doped polyaniline compound. GIXRD results confirmed deposition of an inhibitor film on metal surface within the scratched part of epoxy composite coating filled with GO-PAni-Zn particles. In addition, the coating surface damage during salt spray test was significantly decreased through addition of GO-PAni-Zn as demonstrated by SEM/contact angle tests.

Mesoporous silica – support for organometallic complex and its enzymes activity inhibition properties

The platinum complex with 2,3-disubstituted-1,4-naphthoquinone was evaluated as a potential new anti-ulcer drug, due to its inhibition effect on urease. This complex was supported on the obtained silica and amino-mesoporous silica with typical structure and texture. Presence of the amine group and platinum complex on the silica materials was confirmed by FT-IR measurements. Determination of the urease activity was made with Nessler reagent. The obtained results evidenced a high inhibitor effect on urease activity. This effect was diminished after platinum complex immobilization on mesoporous silica. Although the inhibitor effect of platinum complex on urease activity decreased, it was evidenced its stability after immobilization on silica mesoporous supports. This is the consequence of a longer releasing time for platinum complex immobilized on mesoporous silica, more significant for sample supported on amino-mesoporous silica

Construction of a highly effective self-repair corrosion-resistant epoxy composite through impregnation of 1H-Benzimidazole corrosion inhibitor modified graphene oxide nanosheets (GO-BIM)

The aim of this study is to construct a highly effective corrosion resistant epoxy coating with excellent self-repair and active corrosion inhibition properties. For this goal, the graphene oxide (GO) nanosheets were non-covalently functionalized with 1H-Benzimidazole (BIM) molecules. The morphology and chemistry of GO-BIM composite were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It was found from the electrochemical tests results that inclusion of 0.1% GO-BIM into the epoxy coating provided an effective corrosion-resistant system with remarkably enhanced barrier and active inhibition properties, simultaneously.

New organometallic complex supported on mesoporous silica and its enzymes activity inhibition properties

An organometallic platinum complex with 2,3‐disubstituted‐1,4‐naphthoquinonewas evaluated as a potential new anti‐ulcer drug, due to its inhibition effect on urease. This complex was supported on the obtained SBA‐15 and SBA‐15‐NH2 mesoporous silica with typical structure and texture. Presence of the amine group and the organometallic complex on the silica materials was confirmed by FT‐IR measurements. Determination of the urease activity was made with Nessler reagent. The obtained results evidenced a high inhibitor effect on urease activity. This effect was diminished after Pt complex immobilization on mesoporous silica. Although the inhibitor effect of Pt complex on urease activity decreased, it was evidenced its stability after immobilization on silica mesoporous supports. This is the consequence of a longer releasing time for Pt complex immobilized on mesoporous silica, more significant for sample supported on SBA‐15‐NH2.

Anti-corrosion performance of an epoxy ester coating filled with a new generation of hybrid green organic/inorganic inhibitive pigment; electrochemical and surface characterizations

In this study the effect of a hybrid organic/inorganic pigment based on zinc acetate-Cichorium intybus L. leaf extract on the corrosion protection properties of an epoxy ester coating were studied. Results of electrochemical impedance spectroscopy (EIS) revealed that the mild steel corrosion was significantly inhibited in the chloride solution in the presence of hybrid pigment extract. Results exhibited that with the increase in immersion time up to 24 h the corrosion inhibition efficiency significantly increased and reached the maximum value of 94%. Results obtained from the scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) techniques confirmed the deposition of inhibitive films on the mild steel surface. Results showed that in the presence of hybrid pigment not only the barrier but also the active inhibition properties of the epoxy ester coating were effectively enhanced. The low frequency impedance value of the epoxy ester coating was increased in the presence of hybrid pigment, indicating the role of pigment on the coating barrier action enhancement. The increase in charge transfer resistance of the epoxy ester coating with artificial scratch depicted the active inhibition role of the hybrid pigment.

Screening the anti-corrosion effect of a hybrid pigment based on zinc acetyl acetonate on the corrosion protection performance of an epoxy-ester polymeric coating

In this study an epoxy-ester coating was filled with zinc acetyl acetonate (ZnAA). The active corrosion inhibition properties of the ZnAA pigment were studied by electrochemical noise (EN), electrochemical impedance spectroscopy (EIS) and polarization techniques. Also, the surface morphology and composition of the steel panels were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrochemical measurements revealed the effective corrosion inhibition properties of the ZnAA pigment in the solution phase. Polarization test results revealed that in the presence of ZnAA both cathodic and anodic current densities decreased. In fact, the Zn2+ cations and acetyl acetonate anions formed inhibitive films based on Fe2+-acetyl acetonate and zinc oxide/hydroxide complexes on the anodic and cathodic regions. Results of theoretical ab initio quantum mechanics and molecular dynamics simulations evidenced that the inhibitors strongly adsorbed to iron surface through donor–acceptor interactions. The EIS results showed that the epoxy-ester coating protection performance was significantly enhanced by addition of ZnAA hybrid pigment. The ZnAA pigment enhanced the barrier performance of the coating and provided active inhibition properties.

Electrochemical Investigations of the Corrosion Protection Properties of an Epoxy-Ester Coating Filled with Cerium Acetyl Acetonate Anticorrosive Pigment

The corrosion inhibition properties of cerium acetyl acetonate (CeAA) in solution phase were studied by various electrochemical techniques including electrochemical noise (EN), electrochemical impedance spectroscopy (EIS) and polarization test. The EIS and EN tests results demonstrated effective corrosion inhibition properties of cerium acetyl acetonate in solution phase on mild steel. Polarization test results revealed that the CeAA could inhibit both anodic and cathodic reactions. The partial solubility of CeAA in the 3.5 wt% NaCl solution resulted in the formation of active Ce3+ cations and cerium acetyl acetonate anions which adsorbed and formed inhibitive films based on cerium oxide/hydroxide on the cathodic regions and Fe2+-cerium acetyl acetonate complex on the anodic sites. Moreover, the EIS results revealed that incorporation of CeAA pigment into epoxy-ester coating provided good corrosion-protective performance. Not only the barrier performance but also the active inhibition properties of the coating were improved in the presence of CeAA pigment.