Weak Chemical Bonds Research Articles

Induced Changes in Aroma Compounds of Foods Treated with High Hydrostatic Pressure: A Review.

Since conventional thermal processing can have detrimental consequences on aroma compounds, non-thermal technologies such as high hydrostatic pressure (HHP) have been explored. HHP may alter the weak chemical bonds of enzymes. These changes can modify the secondary, tertiary, and quaternary structures of key enzymes in the production of aroma compounds. This can result in either an increase or decrease in their content, along with reactions or physical processes associated with a reduction of molecular volume. This article provides a comprehensive review of HHP treatment’s effects on the content of lipid-derived aroma compounds, aldehydes, alcohols, ketones, esters, lactones, terpenes, and phenols, on various food matrices of vegetable and animal origin. The content of aldehydes and ketones in food samples increased when subjected to HHP, while the content of alcohols and phenols decreased, probably due to oxidative processes. Both ester and lactone concentrations appeared to decline due to hydrolysis reactions. There is no clear tendency regarding terpenes concentration when subjected to HHP treatments. Because of the various effects of HHP on aroma compounds, an area of opportunity arises to carry out future studies that allow optimizing and controlling the effect.

Enhanced SOx sensing performance of BC3 nanosheets functionalized with Na atoms: A first-principles study

Density functional theory calculations were performed to explore the interaction of gas molecules, including SO2 and SO3 with Na-functionalized C3B monolayers. Firstly, the electronic and geometric properties of Na-adsorbed C3B monolayers were examined to search for the most stable metal functionalized C3B based systems. The Na adatoms prefer the hollow site of the C-hexagon of C3B monolayer. Based on the charge density difference calculations, the electronic densities were depleted on the adsorbed Na metals. Thus, the adsorbed Na metals behave as charge donors. Contrary to the pure C3B monolayer with semiconducting property, the Na-adsorbed systems represent metallic character. The considered SO2 and SO3 gas molecules were adsorbed on the metal site of Na-functionalized C3B nanosheets through weak chemical bonds, which indicates the promising media for gas sensing and adsorption. The effects of van der Waals (vdW) interactions were taken into account for the adsorption of gas molecules on the considered C3B sheets. Thus, our results showed that Na-functionalized C3B sheet is a suitable material for gas sensing in the environment.

(Invited) Amorphous Zinc Oxysulfide Thin Films: Synthesis, Physical Properties, and TFT Application

Amorphous oxide semiconductors (AOSs) have been under extensive research during recent years. Because of their high electron mobility even under amorphous state, they have been widely used as key materials for flat panel displays and flexible electronics devices, especially as channel layer of thin film transistor (TFT). Recently, it has been reported that an amorphous mixed-anion semiconductor consisting of only earth-abundant elements, zinc oxynitride (a-ZnON), shows high electron mobility and capability to TFT application [1]. However, a-ZnON is unstable in air due to weak chemical bonds between Zn and N [2]. To overcome this drawback, we synthesized another earth-abundant amorphous mixed-anion semiconductor, amorphous zinc oxysulfide (a-ZnOS) thin films and found that their electron mobility is comparable to those of conventional AOSs (~15 cm2V-1s-1), in addition to good chemical stability under ambient conditions [3]. Successively, a-ZnOS based TFTs were fabricated with bottom-gate and top contact configuration. a-ZnOS thin films with S/(S+O) = ~0.30 shows obvious TFT performance in the pristine states, although their field effect mobility (μ FE) was moderate (μ FE <1 cm2V−1s−1). μ FE increased with the decrease of S/(S+O), but the carrier density became too large for TFT operation. By annealing these films in vacuum at 150 °C for 10 min, their TFT performance was significantly improved; on/off ration over 104 and μ FE over 10 cm2V−1s−1.[1] Kim et al., Sci. Rep. 3, 1459 (2013).[2] Lee et al. Appl. Phys. Lett. 107, 122105 (2015)[3] Y.Zhu et al., Adv. Electron. Mater. 6, 1900602 (2019).

Py-FTIR-GC/MS Analysis of Volatile Products of Automobile Shredder Residue Pyrolysis.

Automobile shredder residue (ASR) pyrolysis produces solid, liquid, and gaseous products, particularly pyrolysis oil and gas, which could be used as renewable alternative energy resources. Due to the primary pyrolysis reaction not being complete, the yield of gaseous product is low. The pyrolysis tar comprises chemically unstable volatiles before condensing into liquid. Understanding the characteristics of volatile products will aid the design and improvement of subsequent processes. In order to accurately analyze the chemical characteristics and yields of volatile products of ASR primary pyrolysis, TG–FTIR–GC/MS analysis technology was used. According to the analysis results of the Gram–Schmidt profiles, the 3D stack plots, and GC/MS chromatograms of MixASR, ASR, and its main components, the major pyrolytic products of ASR included alkanes, olefins, and alcohols, and both had dense and indistinguishable weak peaks in the wavenumber range of 1900–1400 cm−1. Many of these products have unstable or weaker chemical bonds, such as =CH–, =CH2, –C=C–, and –C=CH2. Hence, more syngas with higher heating values can be obtained with further catalytic pyrolysis gasification, steam gasification, or higher temperature pyrolysis.

Unique amorphous manganese oxide/rGo anodes for lithium-ion batteries with high capacity and excellent stability

The utilization of manganese oxide anode materials in lithium-ion batteries is hindered by low conductivity, high stress/strain, volume expansion, and high over potential in the crystalline structure during cycling. Compared with crystal oxide, amorphous oxide has attracted attention for its weak chemical bond force and its low stress change during the phase change process, but few reported in lithium-ion batteries. This work combined both advantages of amorphous manganese oxide (AMO) and reduced graphene oxide (rGo) to produce a unique AMO/rGo composite electrode material through one-step chemical reduction the KMnO4 in graphene oxide containing solution. The rGo-supported porous amorphous structure of manganese oxide brought special character by reducing the stress/strain of the conversion reaction, thus ensuring a high capacity and high stability. The high electronic and lithium-ion conductivity of graphene also enhanced the rate capability. As a result, the as-synthesized AMO/rGo exhibited a large reversible specific capacity (784 mA hg−1 at the current density of 1 A g−1 over 500 cycles) and superior rate capability, making it a potential candidate as high-performance electrode material for long-term cycling in lithium-ion batteries.

Leading Interaction Components in the Structure and Reactivity of Noble Gases Compounds.

The nature, strength, range and role of the bonds in adducts of noble gas atoms with both neutral and ionic partners have been investigated by exploiting a fine-tuned integrated phenomenological–theoretical approach. The identification of the leading interaction components in the noble gases adducts and their modeling allows the encompassing of the transitions from pure noncovalent to covalent bound aggregates and to rationalize the anomalous behavior (deviations from noncovalent type interaction) pointed out in peculiar cases. Selected adducts affected by a weak chemical bond, as those promoting the formation of the intermolecular halogen bond, are also properly rationalized. The behavior of noble gas atoms excited in their long-life metastable states, showing a strongly enhanced reactivity, has been also enclosed in the present investigation.

Spin-Current Control by Induced Electric Polarization Reversal in Ni/hBN/Ni: A Cross-Correlation Material

We undertook an ab-initio study of hexagonal boron nitride (hBN) sandwiched between Ni(111) layers to examine the interface of this material structure. We considered Ni(111)/hBN/Ni(111) with a slab with three Ni atomic layers to determine the exact atom arrangement at the interface. The density functional theory calculations for 36 stacking arrangements, which are doubled with respect to the magnetic alignment of slabs in an anti-parallel configuration (APC) and parallel configuration (PC), revealed that the number of formed weak chemical bonds, in the pd-hybridization between the N and Ni atoms, is decisive. A maximum of two pd-hybridization bonds stabilized the structure, with APC proving to be the most favorable magnetic alignment, in line with the results of previous experimental studies. In the lowest energy state, an induced magnetic moment at an N site appears when N is moved closer to one of the Ni atoms. Interestingly, the moment direction is switched by the position of the N layer in the resulting bi-stable state with electrical polarization when APC is chosen. The transmission probability calculation of Ni/hBN/Ni having the determined interface structure at the center of the junction exhibits a spin-filtering effect where the spin-polarized current is controlled by the electric field when a field-induced reversal of the polarization is realized.

Features of electronic polarizability and approach to unique properties in tellurite glasses

AbstractTellurite glasses showing unique properties such as low phonon energy and high linear and nonlinear optical properties have been considered as promising materials for photonic device applications. The present article reviews the current status of the electronic polarizability in binary and ternary tellurite glasses and approaches their unique properties. Tellurite glasses consisting of basic modifier oxides (eg, Na2O, ZnO) and basic conditional glass forming oxide (TeO2) exhibit the features of high electronic polarizability and weak chemical bond strength, that is, refractive index‐based large oxide ion polarizability αO2‐(no), large optical basicity ∧(no), small interionic interaction parameter A(no), and small single bond strength BM‐O. The values of αO2‐(no), ∧(no), and A(no) in several tellurite glasses containing WO3, Nb2O5, and Bi2O3 were estimated in this article, and a good correlation was confirmed between ∧(no) and A(no). Unique properties of low glass transition temperature, fragile structural relaxation behavior, poor mechanical properties, high third‐order nonlinear optical susceptibilities in tellurite glasses were discussed from the point of electronic polarizability.

Preparation and adsorption characteristics of rosin-based polymer microspheres for berberine hydrochloride and separation of total alkaloids from coptidis rhizoma

Abstract Coptidis rhizoma, the dried rhizome of the plant Coptis, is a source of potentially valuable alkaloids, including berberine hydrochloride (BBH). However, extraction of these compounds is challenging, and existing resins for adsorption-based separation and purification are based on synthetic compounds, which can leach into the product. Therefore, we prepared separation microspheres from a natural compound. The rosin-based polymer microspheres (RBPMs) were synthesized using ethylene glycol maleic rosinate acrylate as a cross-linker and methacrylic acid as a functional monomer. The physical and chemical properties of the RBPMs were characterized by different analytical techniques. The RBPMs had a clean surface, narrow particle size distribution, mesoporous structure, and good thermal stability. BBH was adsorbed onto the RBPMs very efficiently, and the adsorption process was fitted well to the pseudo second-order kinetics, intra-particle diffusion, and Langmuir isotherm model. The thermodynamic parameters indicate that the adsorption process was spontaneous, exothermic, physical, and involved weak chemical bonds. The comprehensive analysis of experimental results suggested that the ion exchange may drive the uptake process of BBH. Dynamic adsorption and desorption tests revealed that the dynamic adsorption capacity of BBH on RBPMs was 612.4 mg/g. Moreover, the separation capability of RBPMs for concentrating coptidis total alkaloids was established using chromatographic column breakthrough experiments, and the content of coptidis total alkaloid increases from 34.2% to over 91.0%. These results suggested that RBPMs are a very promising polymeric adsorption material for concentrating coptidis total alkaloids and purifying BBH from the coptidis rhizoma extracts.

Adsorption damage of hydroxypropyl guar gum to porous media composed of quartz

Hydroxypropyl guar gum (HPG) is widely used in the hydraulic fracturing of sand rock gas reservoirs. The HPG residue can severely damage the rock surface of the reservoirs owing to the interaction between the HPG molecular chain and the rock surface, which results in adsorption and retention of HPG. To confirm the interaction between HPG and rock, the adsorption properties of HPG on a rock surface were investigated. The dependence of HPG adsorption on HPG concentration, pH, and temperature is discussed, and the adsorption force between HPG and quartz is also studied. With an increase in HPG concentration and pH, the amount of adsorbed HPG increases. The amount of adsorption increases first with temperature and then decreaseds. According to infrared spectroscopy and Zeta potential results, there is a weak chemical bond between HPG and quartz particles. Hydrogen bonding is the main force, which results in the adsorption and retention of HPG in porous media.

Crystallization Kinetics of Water on Bare, Hydrogenated, and Hydroxylated Si(100) and Si(111) Surfaces Studied by RHEED, TOF-SIMS, and TPD

Nucleation and growth processes of water deposited onto Si(100) and (111) substrates were investigated in terms of the influences of hydrogenation and hydroxylation of the surface, as well as high-energy electron-beam irradiation. On the hydrogenated Si(100) substrate, randomly oriented ice Ic crystallites grow by heating a monolayer of amorphous solid water (ASW) to ca. 150 K after agglomeration into droplets at T > 80 K. In contrast, nucleation of the ASW monolayer is strongly prohibited on the hydroxylated Si(100) substrates; crystallites are formed in the multilayer regime out-of-registry with the substrate as a result of spontaneous nucleation. The epitaxial growth is quenched on the hydroxylated Si(100) surface (bare Si(100)-(2 × 1) surface) because water molecules bound tightly to the substrate via hydrogen bonds (weak chemical bonds) control the ice nucleation in contrast to the physisorbed water species. On the other hand, the epitaxial growth (nonepitaxial growth) of ice is observed even at 100 ...

Influence of Temperature‐Dependent Substrate Decomposition on Graphene for Separable GaN Growth

AbstractGraphene has been adopted in III−V material growth since it can reduce the threading dislocations and the III−V epilayer can easily be separated from the substrate due to the weak chemical bond. However, depending on the substrate supporting the graphene, some substrates decompose in the III−V material growth environment, which results in the problem that no graphene remains. In this study, the influence of temperature‐dependent substrate decomposition on graphene through an annealing process that resembles conventional growth conditions in metal–organic chemical vapor deposition (MOCVD) is investigated. It is also confirmed that trimethylgallium, hydrogen, and ammonia gases do not directly affect the graphene loss through gallium nitride (GaN) growth on a graphene/sapphire. In addition, GaN grown on graphene/sapphire could separate, but GaN grown on a graphene/GaN template could not be separated due to GaN template decomposition and related graphene damage. Through further investigation for graphene/gallium arsenide, it is deduced that the gallium generated by substrate decomposition does not play a major role in damage to the graphene but instead the nitrogen generated by substrate decomposition is closely related to it. These results suggest that it is very important to adopt a decomposition‐free substrate that do not damage graphene during GaN growth in MOCVD.

Interface Bonding Mechanism of Recycled Asphalt Mixture

With more and more asphalt pavement entering into maintenance period, a large number of aged and damaged asphalt pavements are excavated to reclaimed asphalt pavement. Recycling of old asphalt pavement into asphalt mixture is one of the important ways to solve this kind of waste material. However, the water stability of reclaimed asphalt mixture is difficult to meet the requirements of actual pavement performance, resulting in insufficient pavement durability. Water vapor weakens the bond between asphalt and aggregate and asphalt paste. In this paper, the failure mechanism of interfacial bond in asphalt mixture is summarized by using weak boundary layer, electrostatic force, chemical bond, mechanical bonding and surface free energy from the view of microstructure. Further more, the research direction of interfacial bonding mechanism of recycled asphalt mixture is put forward.

Origin of Intrinsically Low Thermal Conductivity in Talnakhite Cu17.6Fe17.6S32 Thermoelectric Material: Correlations between Lattice Dynamics and Thermal Transport.

Understanding the nature of phonon transport in solids and the underlying mechanism linking lattice dynamics and thermal conductivity is important in many fields, including the development of efficient thermoelectric materials where a low lattice thermal conductivity is required. Herein, we choose the pair of synthetic chalcopyrite CuFeS2 and talnakhite Cu17.6Fe17.6S32 compounds, which possess the same elements and very similar crystal structures but very different phonon transport, as contrasting examples to study the influence of lattice dynamics and chemical bonding on the thermal transport properties. Chemically, talnakhite derives from chalcopyrite by inserting extra Cu and Fe atoms in the chalcopyrite lattice. The CuFeS2 compound has a lattice thermal conductivity of 2.37 W m-1 K-1 at 625 K, while Cu17.6Fe17.6S32 features Cu/Fe disorder and possesses an extremely low lattice thermal conductivity of merely 0.6 W m-1 K-1 at 625 K, approaching the amorphous limit κmin. Low-temperature heat capacity measurements and phonon calculations point to a large anharmonicity and low Debye temperature in Cu17.6Fe17.6S32, originating from weaker chemical bonds. Moreover, Mössbauer spectroscopy suggests that the state of Fe atoms in Cu17.6Fe17.6S32 is partially disordered, which induces the enhanced alloy scattering. All of the above peculiar features, absent in CuFeS2, contribute to the extremely low lattice thermal conductivity of the Cu17.6Fe17.6S32 compound.

Adsorption differences of sodium oleate on siderite and hematite

To separate siderite from carbonate-bearing iron ore efficiently, specific adsorption configurations and effective species were investigated to compare the adsorption differences of sodium oleate (NaOL) on siderite and hematite surfaces. The species were analysed in neutral conditions, under which the direct flotation of siderite from hematite and quartz was carried out. Changes in the zeta potential, Fourier-transform infrared spectroscopy spectra and X-ray photoelectron spectroscopy spectra caused by the adsorption of oleate species were compared to confirm the adsorbed species on siderite and hematite. Molecular dynamics simulations were carried out to further verify the specific adsorption configurations. Chemisorption of oleate species was detected on both siderite and hematite. The differences in the relative concentration changes of the elements indicate that NaOL worked on siderite and hematite via adsorption of various groups or species. The main functional species were RCOO− for siderite and RCOOHRCOO− for hematite. A strong chemical bond formed as RCOO− directly acted upon the Fe of siderite. The carbon chains bent and interweaved to form the hydrophobic layer on siderite. The two chains of RCOOHRCOO− laid upon hematite via weak chemical bonds and hydrogen bonds. Van der Waals and hydrophobic forces were the main interforces of the two chains.

Co-pyrolysis characteristics and synergistic mechanism of low-rank coal and direct liquefaction residue

ABSTRACTIn this study, the co-pyrolysis of low-rank pulverized coal (SJC) and direct liquefaction residue (DCLR) was comparatively examined. The structure and composition of tar and the evolution characteristics of gas during pyrolysis were analyzed through GC-MS, TG-FTIR, and other analytic techniques. Results showed that SJC+DCLR co-pyrolysis exhibited a significant synergistic effect. SJC and DCLR served as hydrogen donors to facilitate the hydrogenation of small molecular free radical fragments through pyrolysis, which increased the tar yield by 5.55%. Aromatic hydrocarbon and phenol contents in tar decreased by 11.88% and 7.94%, respectively, and alkane content increased by 12.25%. H2 content in gas decreased by 19.05%, and CH4 content increased by 19.60%. Co-pyrolysis could be divided into three stages. In the first stage, adsorbed water and CO2 were removed at room temperature to 344.91°C, and the weak chemical bond between SJC and DCLR began to break. In the second stage, SJC and DCLR became pyrolyzed, small molecular free radical fragments were hydrogenated, large amounts of tar and small-molecule gases were produced at 344.91–643.35°C, and synergistic effect was primarily observed. In the third stage, condensation reaction occurred between small molecular free radical fragments at 643.35–845.75°C, thereby producing solid coke and a small amount of gas.

High-Throughput Open-Air Plasma Activation of Metal-Oxide Thin Films with Low Thermal Budget.

Sputter-processed oxide films are typically annealed at high temperature (activation process) to achieve stable electrical characteristics through the formation of strong metal-oxide chemical bonds. For instance, indium-gallium-zinc oxide (IGZO) films typically need a thermal treatment at 300 °C for ≥1 h as an activation process. We propose an open-air plasma treatment (OPT) to rapidly and effectively activate sputter-processed IGZO films. The OPT effectively induces metal-oxide chemical bonds in IGZO films at temperatures as low as 240 °C, with a dwell time on the order of a second. Furthermore, by controlling the plasma-processing conditions (scan speed, distance a between plasma nozzle and samples, and gas flow rate), the electrical characteristics and the microstructure of the IGZO films can be easily tuned. Finally, OPT can be utilized to implement a selective activation process. Plasma-treated IGZO thin-film transistors (TFTs) exhibit comparable electrical characteristics to those of conventionally thermal treated IGZO TFTs. Through in-depth optical, chemical, and physical characterizations, we confirm that OPT simultaneously dissociates weak chemical bonds by UV radiation and ion bombardment and re-establishes the metal-oxide network by radical reaction and OPT-induced heat.

Bio-inspired and optimized interlocking features for strengthening metal/polymer interfaces in additively manufactured prostheses

Biomedical and dental prostheses combining polymers with metals often suffer failure at the interface. The weak chemical bond between these two dissimilar materials can cause debonding and mechanical failure. This manuscript introduces a new mechanical interlocking technique to strengthen metal/polymer interfaces through optimized additively manufactured features on the metal surface. To reach an optimized design of interlocking features, we started with the bio-mimetic stress-induced material transformation (SMT) optimization method. The considered polymer and metal materials were cold-cured Poly(methyl methacrylate) (PMMA) and laser-sintered Cobalt-Chromium (Co-Cr), respectively. Optimal dimensions of the bio-inspired interlocking features were then determined by mesh adaptive direct search (MADS) algorithm combined with finite element analysis (FEA) and tensile experiments such that they provide the maximum interfacial tensile strength and stiffness while minimizing the stress in PMMA and the displacement of PMMA at the Co-Cr/PMMA interface. The SMT optimization process suggested a Y-shape as a more favorable design, which was similar to mangrove tree roots. Experiments confirmed that our optimized interlocking features increased the strength of the Co-Cr/PMMA interface from 2.3 MPa (flat interface) to 34.4 ± 1 MPa, which constitutes 85% of the tensile failure strength of PMMA (40.2 ± 1 MPa). Statement of SignificanceThe objective of this study was to improve metal/polymer interfacial strength in dental and orthopedic prostheses. This was achieved by additive manufacturing of optimized interlocking features on metallic surfaces using laser-sintering. The interlocking design of the features, which was a Y-shape similar to the roots of mangrove trees, was inspired by a bio-memetic optimization algorithm. This interlocking design lowered the PMMA displacement at the Co-Cr/PMMA interface by 70%, enhanced the interfacial strength by more than 12%, and increased the stiffness by 18% compared with a conventional bead design, meanwhile no significant difference was found in the toughness of both designs.

A Universal Strategy to Design Superior Water‐Splitting Electrocatalysts Based on Fast In Situ Reconstruction of Amorphous Nanofilm Precursors

The development of efficient bifunctional electrodes with extraordinary mass activity and robust stability is an eternal yet challenging goal for the water-splitting process. Surface reconstruction during electrocatalysis can form fresh-composition electrocatalysts with unusual amorphous phases in situ, which are more active but difficult to prepare by conventional methods. Here, a facile strategy based on fast reconstruction of amorphous nanofilm precursors is proposed for exploring precious-metal-free catalysts with good electronic conductivity, ultrahigh activity, and robust stability. As a proof of concept, an amorphous SrCo0.85 Fe0.1 P0.05 O3- δ (SCFP) nanofilm precursor with weak chemical bonds deposited onto a conductive nickel foam (NF) substrate (SCFP-NF) is synthesized by utilizing a high-energy argon plasma to break the strong chemical bonds in a crystalline SCFP target. The quickly reconstructed SCFP-NF bifunctional catalysts show ultrahigh mass activity of up to 1000 mA mg-1 at an overpotential of 550 mV and extremely long operational stability of up to 650 h at 10 mA cm-2 , significantly overperforming state-of-the-art precious-metal catalysts. Such a strategy is further demonstrated to be a universal method, which can be applied to accelerate the reconstruction of other material systems to obtain various efficient electrocatalysts.

EGG WHITE ALBUMIN FORM COMPLEX WITH ASPIRIN AND CAFFEINE AND ITS ROLE AS FREE RADICAL SCAVENGER

Objective: Egg white protein (ovalbumin) is well known to be freshly consumed in Indonesia as traditional medicine, or it is usually known as “Jamu.” Ovalbumin, as well as egg white albumin, is able to form complex compounds with other substances through the formation of weak chemical and physical bonds. The objective of this study is to understand the behavior of ovalbumin as radical scavenger when it binds to antioxidants such as aspirin and caffeine (as a complex). Methods: In this study, docking sites and ovalbumin as scavenger were studied using computer-modeling software. An ovalbumin was used only for computer modeling, whereas in the wet laboratory, the freeze-drying albumin was used for electron spin resonance (ESR) and Fourier transform-infrared (FTIR) spectroscopy to determine its ability as a scavenger and functional groups, respectively. Albumin solution was applied to measure the viscosity. Results: The variability of tridimensional structures of aspirin was investigated after binding with ovalbumin. However, these structures cannot be seen clearly on caffeine. The root-mean-square deviation analysis showed that aspirin, as well as caffeine, altered the dynamic conformation of ovalbumin. The complex of aspirin-ovalbumin-caffeine which was treated at a temperature of −70°C showed intermolecular force. ESR results showed that the complex compounds could effectively reduce more free radicals when compared to aspirin or caffeine. The existence of aromatic compounds (as confirmed by FTIR) was useful for the scavenger molecules and chemical interaction occurs. The viscosity of the complex was similar with normal gastric mucus, which associated with radical scavenger. Conclusion: The characters of albumin when it binds to aspirin and caffeine indicated that scavenging activity of the complex and the viscosity showed an important result to be physiological scavengers of free radicals.