Appearance Of Functional Groups Research Articles

Cellulose nanocrystals from celery stalk as quercetin scaffolds: A novel perspective of human holo-transferrin adsorption and digestion behaviours.

In this study, cellulose nanocrystals (CNCs) were synthesized from celery stalks to be used as the platform for quercetin delivery. Additionally, CNCs and CNCs-quercetin were characterized using the results of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential, while their interactions with human holo-transferrin (HTF) were also investigated. We examined their interaction under physiological conditions through the exertion of fluorescence, resonance light scattering, synchronized fluorescence spectroscopy, circular dichroism, three-dimensional fluorescence spectroscopy, and fluorescence resonance energy transfer techniques. The data from SEM and TEM exhibited the spherical shape of CNCs and CNCs-quercetin and also, a decrease was detected in the size of quercetin-loaded CNCs from 676 to 473 nm that indicated the intensified water solubility of quercetin. The success of cellulose acid hydrolysis was confirmed based on the XRD results. Apparently, the crystalline index of CNCs-quercetin was reduced by the interaction of CNCs with quercetin, which also resulted in the appearance of functional groups, as shown by FTIR. The interaction of CNCs-quercetin with HTF was also demonstrated by the induced quenching in the intensity of HTF fluorescence emission and Stern-Volmer data represent the occurrence of static quenching. Overall, the effectiveness of CNCs as quercetin vehicles suggests its potential suitability for dietary supplements and pharmaceutical products.

Influence of the structure of quinoline derivatives on their sorption on hypercrosslinked polystyrene

The article is devoted to the study of the chromatographic behaviour of quinoline and tetrahydroquinoline derivatives. The purpose of the study was to investigate the patterns of sorption of these compounds from aqueous-acetonitrile solutions on hyper-cross-linked polystyrene using reverse-phase high-performance liquid chromatography. The volume, polarizability, lipophilicity, and dipole moment of molecules of quinoline derivatives were calculated, which significantly depended on the nature and position of functional groups and substituents in the main nucleus. It has been established that the appearance of functional groups and substituents leads to an increase in the volume and polarizability of the molecules of quinoline derivatives compared to unsubstituted quinoline and methylquinoline, while the lipophilicity and dipole moment change depending on the nature of the substituent and its position in the main fragment. The dependences of sorption characteristics on the structure and physicochemical properties of sorbates were obtained. It has been shown that, in accordance with the laws of the reversed-phase version of liquid chromatography, the retention of substances changes symbatically with the change in the characteristics of the molecules responsible for dispersion interactions. In this case, the presence in the molecules of halogen atoms, phenyl radicals and other substituents capable of π-interactions with the surface of hyper-cross-linked polystyrene led to a significant increase in retention, and the presence of a carboxyl group or carboxyalkyls prone to interaction with the polar eluent significantly weakens retention. The appearance of an ester group in sorbate molecules generally significantly increased the volume, polarizability and lipophilicity of the corresponding derivatives, but had virtually no effect on retention, and therefore it was suggested that the presence of a carbonyl oxygen atom, capable of interacting with the polar components of the eluent, neutralizes the effect of physical-chemical factors that determine the sorption of these substances due to dispersion interactions. Thus, despite the symmetry in changes in the physicochemical parameters of the studied compounds and their retention, there was no strict proportionality, since, on the one hand, the retention of sorbates was carried out in accordance with the change in their physicochemical parameters, and on the other hand, it was determined by the tendency molecules of these compounds to competitive interactions with the components of the mobile phase. The presented results of the study can be useful in the development and optimization of methods for analysing compounds with similar structures, as well as for developing the theory of sorption of polyfunctional compounds from multicomponent solutions and establishing the relationship between sorption characteristics, other physicochemical parameters and the structure of molecules.

Effect of pyrolysis temperature on the physiochemical properties of biochar and its potential use in anaerobic digestion: A critical review

A comprehensive study was conducted to assess the influence of pyrolysis temperature (PyT) on the properties of biochar (BC) and its potential application in anaerobic digestion (AD). PyT is an essential parameter for effectively utilizing BC in full-scale AD, because PyT can develop BC properties that are necessary for improving AD performance through (I) the increment of BC porosity, (II) the adsorption and conversion of metabolites, (III) the enrichment of microbial communities, and (IV) the enrichment of functional groups. Some features of BC, such as porosity, electrical conductivity, and pore structure, increase consistently with increasing PyT. These properties have a positive effect on AD and enhancement of methane yield. The adsorption of excessive metabolites correlates with the enrichment of BC functional groups. The appearance of functional groups of BC decreases when the PyT increases. No substantial correlation (R2 < 0.1) could be found between the enhancement of methane yield and the enrichment of BC functional groups and the adsorption capacities of BC. Microbial communities are positively correlated to the increment of PyT with a moderate correlation (R2=0.33) to the enhancement of methane yield. The review also identifies several knowledge gaps that necessitate further investigation.

Phospate Release Study on Silica Gel and Amino Silica Hybrid Sorbent from Lapindo Mud

This study discusses the rate of phosphate release in Silica Gel (SG) and Amino Silica Hybrid (ASH) sorbents using Lagergren pseudo-first Order Kinetic and Lagergren Pseudo-second Order Kinetic. ASH synthesis was done by adding a 3-aminopropyltriethoxysilane (APTES) modifier to sodium silicate from Lapindo Mud. Phosphate binding was carried out at 30 minutes with a stirring speed of 250 rpm. Analysis using IR spectrophotometer showed the success of ASH synthesis as indicated by the appearance of functional groups -NH2 and -CH2 at wavenumbers 1635 cm-1 and 1473 cm-1. With the continuous method, SG and ASH sorbents that have bound phosphate were then desorbed at various times of 2, 3, 4, 7, 8, and 9 days. The amount of phosphate anion released from SG and ASH was tested using a UV-Vis instrument then modeling was carried out to determine the rate of phosphate release. The desorption results showed the amount of phosphate released from the ASH sorbent was less than that of the SG sorbent. Through modeling, the proceeds of the phosphate release rate follow the Lagergren Pseudo-second Order Kinetic with an experimental QE of 0.22089 M/g for SG sorbent and 0.33333 M/g for ASH sorbent.

Removal and recyclable chitosan nanowires: Application to water soluble dyes

In this research experiment, the potential of chitosan nanowires for the removal of cationic dyes which were Methylene Blue (MB) and Reactive Red l41 (RR-141) from wastewater was investigated. Chitosan powder was prepared from shrimp shells, then, chitosan nanowires were synthesized with the ionic gelation method, using sodium tripolyphosphate as a crosslinking agent under mild conditions. The appearance of functional groups of pure chitosan nanowires, together with 81% degree of acetylation and 110.2 m2 g−1, were achieved. TEM image revealed the incorporation of dye within the chitosan structures. The adsorption capacity was affected significantly by the amount of chitosan present, contact time, pH and dye concentration. The highest removal rates of MB and RR-141 were 91.5% and 82.74% respectively, within 60 min with dye solution of 75 mg L−1 at pH 4 and 10 g chitosan, and the uptake capacity remained around 82.3–91.5% for 3 regeneration cycles. The adsorption isotherm correlated well with Langmuir and the Freundlich isotherms. Therefore, eco-friendly bio-chitosan could be applied successfully for dye contaminated wastewater remediation. Rather than a lab scale, further commercial process should be applied for higher effective performances.

Optical and dielectric studies of PMMA: precursors of BNT hybrid films

In this study, polymethyl methacrylate (PMMA)-based organic–inorganic hybrid films were deposited by the sol–gel technique by mixing the methyl methacrylate (MMA) organic precursor solution with an inorganic precursor solution of bismuth sodium titanate (Bi0.5Na0.5TiO3 or commonly known as BNT). 3-(trimethoxysilyl) propyl methacrylate (TMSPM) was used as coupling agent to improve the compatibility between the phases. The chemical composition and thermal stability were monitored by FTIR spectroscopy and thermogravimetric analysis. The high thermal stability observed together with the appearance of functional groups related to Si–O–metal interactions confirms the formation of a hybrid organic–inorganic material. A study of the optical properties by UV–Vis was also performed, where the refractive index between 2.1 and 2.6 was obtained, corroborating a good coupling between the organic and inorganic phases in the hybrid films. Atomic force microscopy measurements were also made to determine the surface morphology and roughness of the hybrid films and bear out their homogeneity. Finally, electrical measurements were performed by capacitance–voltage (C–V) and current–voltage (I–V), to obtain the dielectric permittivity constant with values from 15.5 to 18.5 and density current from 1 × 10−5 to 1 × 10−6 A cm−2. In comparison with other PMMA-based hybrid materials such as those containing the precursors TiO2 or SiO2, the PMMA–BNT hybrid material shows an improvement in its optical and dielectric properties.

Surface Energy Characteristics of Polytetrafluoroethylene Bombarded with MeV Protons

Energy characteristics of the irradiated surface of a polytetrafluoroethylene film depend on the energy and fluence of bombarding MeV protons. Irradiation with 2–4 MeV protons leads to an increase in the surface free energy; 4 MeV protons at a fluence of 1015 proton/cm2 increase the polarity of the polymer surface by 40 times due to the appearance of functional groups, the polarity enhancement being manifested in an increase in the acid–base component of the surface energy by more than a factor of 50. There is a correlation between the dispersion component of the surface energy and the degree of crystallinity of the near-surface layer of the polymer a period. They both grow symbatically in the case of bombardment with 1–2 MeV protons and decrease upon irradiation with 4 MeV protons. It has been found that dehydrofluorination results in carbonization of the irradiated surface, a decrease in the fluorine content, and an increase in the proportion of oxygen due to oxidation of the radicals generated by proton bombardment.

Effect of Accelerated Protons on the Surface Properties of Polyethylene

The irradiation of low-density polyethylene with MeV protons leads to a substantial increase in surface free energy, its acid–base component, and surface polarity due to the appearance of functional groups in the surface layer, as confirmed by ATR IR and Raman spectra. It has been shown that the surface energy of the irradiated polymer depends little on the change in proton energy from 1 to 4 MeV at a fluence of 1015 proton/cm2. It has been found that the oxygen content of the irradiated polymer surface increases as a result of oxidative reactions of the radicals generated during radiolysis and the thermal stability of the polymer decreases.

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TST and TSG groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of APT were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide denture base. Amino-functionalized silica coating could represent a more applicable and convenient option for improving the repair strength of autopolymerizing resin to polyamide polymer.

Curcumin coated gold nanoparticles: synthesis, characterization, cytotoxicity, antioxidant activity and its comparison with citrate coated gold nanoparticles

Objective(s): Biological applications of gold nanoparticles have limitations because of the toxic chemicals used in their synthesis. Curcumin can be used as reducing as well as capping agent in synthesis of GNPs to eliminate the cytotoxicity. Conjugation of curcumin to gold also helps in increasing its solubility and bioavailability. Materials and Methods: Here we report synthesis of gold nanoparticles coated with citrate and curcumin and of two different sizes via chemical routes. UV-Vis absorbance spectroscopy, Dynamic Light Scattering and Transmission Electron Microscopy were applied to study the average particle size, size stability of the samples and zeta potential. Fourier transform infrared, Raman Spectroscopy and Fluorescence Spectroscopy were applied for detection of curcumin on the surface of GNPs. The antioxidant activity was evaluated using DPPH assay and Cytotoxicity was evaluated by MTT assay.Results: Particles were synthesized of 6 and 16 nm size. The average particle size was found to be 21.7 ± 5.7 by TEM. The zeta potential on the surface of Cur-GNPs was negative and larger than 25 mV which is a sign of their high stability. The stability of these particles (with different coatings but with similar sizes) at different time intervals (up to 3 months) and also in different media like cell culture medium, different buffers, glucose and at different pH conditions have been investigated thoroughly. Appearance of functional groups assigned to curcumin in FTIR and SERS spectra are sign of presence of curcumin in the sample. The quenching of the fluorescence in the presence of GNPs reveals the clear indication of the capping and binding of curcumin with GNPs. Cur-GNP1 (16 nm) were found to exhibit highest antioxidant activity than other gold nanoparticles. Cytotoxicity evaluation using MTT assay on L929 cell line proved curcumin coated gold nanoparticles were non-toxic up to 40 ppm.Conclusion: The results revealed that larger curcumin coated gold nanoparticles were stable and also non-toxic and were found suitable for further in-vitro and in-vivo studies.

Modification of polystyrene with a highly reactive cold oxygen plasma

Samples of biaxially oriented polystyrene (PS) were exposed to an extremely non-equilibrium oxygen plasma. The neutral gas kinetic temperature was 70 °C, the electron temperature was about 3 eV, the plasma density was about 2 × 10 15 m − 3 , and the neutral oxygen atom density was 4 × 10 21 m − 3 . The plasma was created with an electrodeless radiofrequency discharge and the samples were kept at a floating potential. The plasma treatment time was between 1 and 50 s. The samples were characterized by high-resolution X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), microbalance, and water contact-angle (WCA) measurements. The etching rate was found to be relatively independent of the treatment time, at about 9 nm/s. The corresponding probability for oxidation with O atoms was calculated from the known flux of O atoms onto the surface, and was close to 6 × 10 − 4 . The AFM did not show any appreciable increase in the surface roughness due to the plasma treatment. Both the XPS and the WCA measurements showed a well-activated surface after just a second of plasma treatment. The rapid functionalization was explained by the huge flux of O atoms onto the sample surface. The tilting of the samples during the XPS characterization made it possible to conclude that the oxygen-containing functional groups were concentrated at the surface of the film, at a depth much smaller than that examined by XPS. The functional groups found using XPS were the standard C–O, O–C–O, C = O, O–C═O as well as –O–CO–O–. The appearance of functional groups with a high degree of oxidation, like carboxyl and carbonate, was attributed to the oxygen's interaction with the aromatic phenyl rings. The ageing results showed that the concentration of the oxygen functional groups did not change much, but the contact angle of the water drop increased moderately during the first day and remained almost unchanged after subsequent ageing.

Background defining during the imine formation reaction in FT-IR liquid cell

Imine formation is a very important chemical reaction because of its relevance to biological process. Therefore, it is crucial to follow whole reaction process in detail. The current work performed to monitor the whole imination reaction in real time in liquid cell by FT-IR spectroscopy. The complex spectral futures due to solvent, unreacted reagents, acid catalysis and other additives are eliminated by defining a background at the beginning or at any time during the reaction. This procedure also makes it possible to monitor the changes in the concentration of each component in the liquid cell. The consumption of the functional groups of the reagents results in absorbance due to the direct difference spectra while the appearance of functional groups is monitored as percentage transmittance. The concentration changes in the cell arising from the reaction gives the product spectra without having to isolate it from the mixture. It is also possible to see the intermediates appearing and disappearing during the reaction. This report also illustrates a brief application of the technique by time dependence of the peak highs in absorption (ABS) mode.

Correlation of base consumption with the degree of hydrolysis in enzymic protein hydrolysis.

It is fairly easy to control the enzymic hydrolysis of proteins in alkaline conditions by measuring the base consumption required to keep the pH constant in the reactor. Unfortunately, however, base consumption is not related in any simple way to the degree of hydrolysis reached at any given moment and to establish this relationship it is essential to find out the mean pK of the alpha-amino groups released during the hydrolytic process. We have shown here that the correct mean pK value varies according to the pH of the working conditions and that the relationship between these values may depend upon the kind of protein and protease used. We have put forward a method for determining this relationship experimentally by using a given protein-protease system, consisting of an alkaline titration of the raw protein and when partially hydrolysed. We have tested the results predicted by our theoretical model by applying it to the hydrolysis of whey proteins with a bacterial protease from Bacillus licheniformis at 50 degrees C, pH 8.0. This model can easily be applied to any hydrolytic process involving the appearance of functional groups that are partially protonizable under the working conditions in question in order to follow the kinetics of the reaction via the consumption of the neutralizing agent required to keep pH constant.