Electronic Resonance Research Articles

Pyrogallol Detection Based on the Cobalt Metal–Organic Framework of Nanomaterial-Enhanced Chemiluminescence

The cobalt metal–organic framework (Co-MOF) is a kind of crystalline porous material within a periodic network structure, which is formed via the self-assembly of a Co metal center and a bridged organic ligand. In this paper, a Co-MOF was facilely synthesized via an ultrasonic method and applied to enhance the chemiluminescence (CL) emission of the NaIO4-H2O2 system. The synthesized Co-MOF was nanosheet-like in nature and stacked in 2–3-micrometer flower shapes. Compared to the NaIO4-H2O2 system without a Co-MOF, the CL intensity of the Co-MOF-NaIO4-H2O2 system was enhanced about 70 times. This CL mechanism was determined to be a result of the synergistic effects of chemiluminescence resonance energy transfer (CRET) and electron–hole annihilation (EHA). The Co-MOF not only acted as a catalyst to accelerate the generation of reactive oxygen species in the CL reaction, but also worked as an emitter to further enhance the CL. Based on the Co-MOF-NaIO4-H2O2 system, a highly sensitive CL analysis method was established for pyrogallol (PG) detection. Addition of PG into the CL system generated 1O2*, which could transfer energy to the Co-MOF and further enhance the CL response. The enhanced CL was linear with the PG concentration. The CL analysis method exhibited a linear range of 1 × 10−4 M to 1 × 10−7 M, as well as having a linear correlation coefficient of 0.9995 and a limit of detection of (S/N = 3) of 34 nM.

Structural Modification and Biological Activity of Polysaccharides.

Natural polysaccharides are macromolecular substances with a wide range of biological activities. The structural modification of polysaccharides by chemical means can enhance their biological activity. This paper reviews the latest research reports on the chemical modification of natural polysaccharides. At present, the modification methods of polysaccharides mainly include sulfation, phosphorylation, carboxymethylation, socialization, methylation and acetylation. The chemical and physical structures of the modified polysaccharides were detected via ultraviolet spectroscopy, FT-IR, high-performance liquid chromatography, ultraviolet spectroscopy, gas chromatography-mass spectrometry, nuclear magnetic resonance and scanning electron microscopy. Modern pharmacological studies have shown that the modified polysaccharide has various biological activities, such as antioxidant, antitumor, immune regulation, antiviral, antibacterial and anticoagulant functions in vitro. This review provides fresh ideas for the research and application of polysaccharide structure modification.

Resonant electron confinement and sheath expansion heating in magnetized capacitive oxygen discharges

In weakly magnetized capacitive radio frequency (RF) plasmas electrons accelerated into the plasma bulk by the expanding RF boundary sheath at one electrode can be returned to this electrode due to their gyromotion around an externally applied magnetic field oriented parallel to the electrodes. If the driving frequency and magnetic field are chosen so that the electron cyclotron frequency, ω ce, equals half of the driving RF, ω rf, such energetic beam electrons will be returned to the sheath during its expansion phase and, thus, will be confined and heated resonantly. This magnetized RF sheath resonance (MRSR) effect is studied based on kinetic particle-in-cell simulations in weakly magnetized capacitively coupled oxygen plasmas. In comparison with electropositive argon plasmas, this resonance mechanism is found to be affected strongly by the electronegativity of oxygen discharges. In the unmagnetized case, low-pressure capacitive oxygen discharges operate in an electropositive mode, where nonlinear high-frequency sheath oscillations play an important role similar to previous observations in electropositive discharges with low electron densities. If the resonance condition is fulfilled (), the discharge efficiency is enhanced due to the MRSR effects, resulting in an increase in plasma density. Our numerical results demonstrate that this resonance effect is particularly efficient at low pressure and low electronegativity. However, in strongly electronegative discharges, the time it takes a typical resonant electron to return to the expanding sheath edge is found to be affected by drift and ambipolar electric fields in the plasma bulk, which cause a deviation from the resonance condition, resulting in a reduction of this type of resonance effect.

The conjugation of serotype 31 pneumococcal polysaccharide and CRM197 in N,N-dimethylformamide

Traditionally, PCV (pneumococcal conjugate vaccine) was prepared by the coupling of aldehyde-activated polysaccharide, with a carrier protein via NaCNBH3 (sodium cyanoborohydride) mediated reductive amination in water. However, the reaction is very slow and may take up to several days, which is a significant burden for pharmaceutical companies. Here we report the detailed reaction process of the reductive amination of structurally reassigned serotype 31 polysaccharide and cross reacting material (CRM197) in an organic solvent (N,N-dimethylformamide, DMF) by using STAB (sodium triacetoxyborohydride). The product has been characterized by size exclusion chromatography, nuclear magnetic resonance and transmission electron microscopy. Compared with the traditional method, the reaction can finish within hours and elicited a comparable immune response. The new strategy has the potential of being applied in the preparation of next-generation polysaccharide conjugate vaccines.

Adsorption and reversible conformational change of a thiophene based molecule on Au(111)

We present a low temperature scanning tunneling microscope investigation of a prochiral thiophene-based molecule that self-assembles forming islands with different domains on the Au(111) surface. In the domains, two different conformations of the single molecule are observed, depending on a slight rotation of two adjacent bromothiophene groups. Using voltage pulses from the tip, single molecules can be switched between the two conformations. The electronic states have been measured with scanning tunneling spectroscopy, showing that the electronic resonances are mainly localized at the same positions in both conformations. Density-functional theory calculations support the experimental results. Furthermore, we observe that on Ag(111), only one configuration is present and therefore the switching effect is suppressed.

Effect of Permeable Crystalline Materials on the Mechanical and Porosity Property of Recycled Aggregate and Recycled Aggregate Concrete.

This study investigates the potential of permeable crystalline materials to improve the properties of recycled aggregates and recycled aggregate concrete (RAC). The use of recycled aggregates in concrete production has gained increasing attention due to environmental and economic benefits. However, the lower quality and poorer durability of recycled aggregates limit their wider application. In this study, three types of recycled aggregates were treated with permeable crystalline materials, and their water absorption and crushing index were compared before and after modification. RAC was then produced using modified recycled aggregates with different substitution rates, and their mechanical properties were evaluated. To investigate the mechanism of permeable crystalline materials modification, the microstructure of the modified RAC was observed using nuclear magnetic resonance and scanning electron microscopy. The results demonstrated that the permeable crystalline materials treatment effectively reduced the water absorption and crushing index of the recycled aggregates. The compressive strength of modified RAC also improved, with a higher modification time leading to higher strength. Furthermore, the pore distribution and microstructural denseness of the modified recycled aggregates and RAC were enhanced, as revealed by the microstructural observations. These findings suggest that permeable crystalline materials modification is a promising method for improving the properties of recycled aggregates and RAC, which could contribute to the sustainable development of the construction industry.

Intermediate Antiparallel Fibrils in Aβ40 Dutch Mutant Aggregation: Insights from Nanoscale Infrared Spectroscopy.

Cerebral amyloid angiopathy (CAA), which involves amyloid deposition in blood vessels leading to fatal cerebral hemorrhage and recurring strokes, is present in the majority Alzheimer's disease (AD) cases. Familial mutations in the amyloid β peptide are correlated to higher risks of CAA and are mostly comprised of mutations at residues 22 and 23. While the structure of the wild-type Aβ peptide has been investigated in great detail, less is known about the structure of mutants involved in CAA and evolutions thereof. This is particularly true for mutations at residue 22, for which detailed molecular structures, as typically determined from Nuclear Magnetic Resonance (NMR) spectroscopy or electron microscopy, do not exist. In this report, we have used nanoscale infrared (IR) spectroscopy augmented with atomic force microscopy (AFM-IR) to investigate structural evolution of the Aβ Dutch mutant (E22Q) at the single aggregate level. We show that in the oligomeric stage, the structural ensemble is distinctly bimodal, with the two subtypes differing with respect to population of parallel β sheets. Fibrils on the other hand are structurally homogeneous, with early-stage fibrils distinctly antiparallel in character, which develop parallel β sheets upon maturation. Furthermore, the antiparallel structure is found to be a persistent feature across different stages of aggregation.

Polyvinylpyrrolidone-Alginate-Carbonate Hydroxyapatite Porous Composites for Dental Applications.

An alternative approach for the currently used replacement therapy in dentistry is to apply materials that restore tooth tissue. Among them, composites, based on biopolymers with calcium phosphates, and cells can be applied. In the present work, a composite based on polyvinylpyrrolidone (PVP) and alginate (Alg) with carbonate hydroxyapatite (CHA) was prepared and characterized. The composite was investigated by X-ray diffraction, infrared spectroscopy, electron paramagnetic resonance (EPR) and scanning electron microscopy methods, and the microstructure, porosity, and swelling properties of the material were described. In vitro studies included the MTT test using mouse fibroblasts, and adhesion and survivability tests with human dental pulp stem cells (DPSC). The mineral component of the composite corresponded to CHA with an admixture of amorphous calcium phosphate. The presence of a bond between the polymer matrix and CHA particles was shown by EPR. The structure of the material was represented by micro- (30-190 μm) and nano-pores (average 8.71 ± 4.15 nm). The swelling measurements attested that CHA addition increased the polymer matrix hydrophilicity by 200%. In vitro studies demonstrated the biocompatibility of PVP-Alg-CHA (95 ± 5% cell viability), and DPSC located inside the pores. It was concluded that the PVP-Alg-CHA porous composite is promising for dentistry applications.

Dissociative electron attachment to gold(I)-based compounds: 4,5-dichloro-1,3-diethyl-imidazolylidene trifluoromethyl gold(I).

With the use of proton-NMR and powder XRD (XRPD) studies, the suitability of specific Au-focused electron beam induced deposition (FEBID) precursors has been investigated with low electron energy, structure, excited states and resonances, structural crystal modifications, flexibility, and vaporization level. 4,5-Dichloro-1,3-diethyl-imidazolylidene trifluoromethyl gold(I) is a compound that is a uniquely designed precursor to meet the needs of focused electron beam-induced deposition at the nanostructure level, which proves its capability in creating high purity structures, and its growing importance in other AuImx and AuClnB (where x and n are the number of radicals, B = CH, CH3, or Br) compounds in the radiation cancer therapy increases the efforts to design more suitable bonds in processes of SEM (scanning electron microscopy) deposition and in gas-phase studies. The investigation performed of its powder shape using the XRPD XPERT3 panalytical diffractometer based on CoKα lines shows changes to its structure with change in temperature, level of vacuum, and light; the sensitivity of this compound makes it highly interesting in particular to the radiation research. Used in FEBID, though its smaller number of C, H, and O atoms has lower levels of C contamination in the structures and on the surface, it replaces these bonds with C-Cl and C-N bonds that have lower bond-breaking energy. However, it still needs an extra purification step in the deposition process, either H2O, O2, or H jets.

METHOD OF LOCAL MARKING OF A METAL SURFACE USING ULTRAFINE MINERAL PARTICLES

The method for local marking of a metal surface with ultrafine particles of minerals are offered. Photoluminescence and electronic acoustic resonance methods have been used to study local marks created by minerals and their mixtures using the technology of mineral coatings. It is shown that local areas of metal samples containing microparticles of minerals produce clear signals in the form of luminescence emission peaks and electronic acoustic resonance damping parameters. Having a set of combinations in the form of various luminescent minerals and their mixtures, technological methods for the introduction of minerals and two measuring systems, it is possible to build a local, fairly easily determined marking with a large set of options.

Experimental study on seepage evolution and microscopic characteristics of initially damaged concrete under variable confining pressure

This study aims to examine the impact of service loading and dry-wet-freeze–thaw environments on the initial damage caused to concrete, and conducts initial damage concrete permeability testing and microscopic characterization under varying confining pressure. The evolution pattern and mechanism of specimen permeability are analyzed using the confining pressure sensitivity coefficient, permeability recovery rate, and causeless radial strain. The results indicate that permeability exhibits nonlinear characteristics during the process of confining pressure loading and unloading. The initial permeability increases with increasing load level and the number of dry-wet-freeze–thaw cycles. The loading process can be divided into a sensitive area, a transition area, an insensitive area, and a steady area, according to the confining pressure sensitivity coefficient. The permeability in the sensitive area decreases the most with the increase of confining pressure, while the permeability in the steady area hardly changes. A smaller permeability recovery rate after confining pressure unloading leads to a larger dimensionless radial strain and lower permeability value. Utilizing nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM), it was observed that the initial damage caused the expansion of microcracks and micropores in the specimen, leading to a subsequent amplification of the seepage channels, ultimately resulting in a substantial increase in the specimen's permeability. When confining pressure is loaded, the internal pore structure of the specimen undergoes elastic–plastic deformation. Upon confining pressure unloading, the proportion of macropores in the specimen decreases by 78.79%, resulting in incomplete restoration of the permeability value.

Interpreting ultrafast electron transfer on surfaces with a converged first-principles Newns-Anderson chemisorption function.

We study the electronic coupling between an adsorbate and a metal surface by calculating tunneling matrix elements Had directly from first principles. For this, we employ a projection of the Kohn-Sham Hamiltonian upon a diabatic basis using a version of the popular projection-operator diabatization approach. An appropriate integration of couplings over the Brillouin zone allows the first calculation of a size-convergent Newns-Anderson chemisorption function, a coupling-weighted density of states measuring the line broadening of an adsorbate frontier state upon adsorption. This broadening corresponds to the experimentally observed lifetime of an electron in the state, which we confirm for core-excited Ar*(2p3/2-14s) atoms on a number of transition metal (TM) surfaces. Yet, beyond just lifetimes, the chemisorption function is highly interpretable and encodes rich information on orbital phase interactions on the surface. The model thus captures and elucidates key aspects of the electron transfer process. Finally, a decomposition into angular momentum components reveals the hitherto unresolved role of the hybridized d-character of the TM surface in the resonant electron transfer and elucidates the coupling of the adsorbate to the surface bands over the entire energy scale.

Efficient degradation of phenol by MnOOH-rGO composite with high peroxymonosulfate utilization efficiency

A high-performance, durable, low-cost, and environmentally friendly catalyst is highly desired in advanced oxidation processes (AOPs) for water treatment. Considering the activity of Mn(Ⅲ) and the superior catalytic properties of reduced graphene oxide (rGO) in peroxymonosulfate (PMS) activation, rGO-modified MnOOH nanowires (MnOOH-rGO) were fabricated by a hydrothermal method for phenol degradation. The results showed that the composite synthesized at 120 °C with 1 wt% rGO dopant exhibited the best performance for phenol degradation. Nearly 100% of the phenol was removed by MnOOH-rGO within 30 min, which is higher than the removal rate of pure MnOOH (70%). The effects of catalyst dosages, PMS concentration, pH, temperature, and anions (Cl−, NO3−, HPO42−and HCO3−) on phenol degradation were investigated. The removal rate of chemical oxygen demand (COD) reached 26.4%, with a low molar ratio of PMS to phenol at 5:1 and a high PMS utilization efficiency (PUE) of 88.8%. The phenol removal rate remained more than 90% after five recycle with less than 0.1 mg L−1 leakage of manganese ions. Together with the results of radical quenching experiments, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR), electron transfer and 1O2 were proved to dominate the activation process. During the direct electrons transfer process, the electrons transfer from the phenol to PMS by using the Mn(Ⅲ) as the mediate with a stoichiometric ratio between PMS and phenol at 1:2, which mainly contributed to the high PUE. This work provides new insight into a high-performance Mn(Ⅲ) based catalyst on PMS activation with high PUE, good reusability, and environmentally friendly for removing organic pollutants.

H-ZSM-5 Catalysts for the catalytic upcycling of polypropylene glycol

Without effective management, the steady increase of waste plastics threatens environmental well-being and ecological balance. Plastic up/recycling is a promising solution but has many challenges. In this work, catalytic cracking of polypropylene glycol (PPG) was investigated at varying reaction temperatures of 350–550 °C under nitrogen and steam, using H-ZSM-5 zeolites with different silica-to-alumina (SiO2/Al2O3) ratios of 23:1 and 50:1. The catalysts were assessed through physisorption, chemisorption, solid-state magic-angle spinning nuclear magnetic resonance spectrometry, thermogravimetry, electron microscopy, and positron annihilation lifetime spectroscopy. Extra framework aluminum and Lewis-to-Bronsted acid site ratios were found to play a significant role in the selectivity towards propionaldehyde, where values ∼ 80 % could be reached. In addition, a possible pathway for the PPG cracking reaction was proposed, which may lead to a better understanding of PPG and waste plastic decomposition via zeolite-based catalysts.

The solid effect of dynamic nuclear polarization in liquids.

The solid-state effect of dynamic nuclear polarization (DNP) is operative also in viscous liquids where the dipolar interaction between the electronic and nuclear spins is partially averaged. The proper way to quantify the degree of averaging, and thus calculate the efficiency of the effect, should be based on the time-correlation function of the dipolar interaction. Here we use the stochastic Liouville equation formalism to develop a general theoretical description of the solid effect in liquids. The derived expressions can be used with different dipolar correlations functions depending on the assumed motional model. At high magnetic fields, the theory predicts DNP enhancements at small offsets, far from the classical solid-effect positions that are displaced by one nuclear Larmor frequency from the electronic resonance. The predictions are in quantitative agreement with such enhancement peaks observed at 9.4 T . These non-canonical peaks are not due to thermal mixing or the cross effect but exactly follow the dispersive component of the EPR line.

Nanocomposite of reduced nanographene oxide with β-lactoglobulin protein (rNGO/β-Lg) as a carrier of the anticancer drug oxaliplatin (Eloxatin)

In this study, reduced nanographene oxide (rNGO) together with β-lactoglobulin (β-Lg) protein is used for better and more effective encapsulation, loading and release of oxaliplatin (OXP) drug in colon tumor cells. Drug distribution, loading and encapsulation on graphene oxide/reduced β-lactoglobulin (rNGO/β-Lg) nanocomposite is investigated and confirmed by IR, Uv-Vis, fluorescence and zeta sizer analysis. The rNGO/β-Lg nanocomposite shows a promising loading capacity. So that the percentage of encapsulation and loading for the anticancer drug oxaliplatin is 70 % and 55 %, respectively, and the results show that the penetration and diffusion mechanism is non-Fickian diffusion. Due to the electronic stereo resonance of the drug with the nanocomposite, rNGO/β[email protected] has low toxicity in healthy tissues and higher toxic effects on colon cancer cells than the free oxaliplatin drug. The interaction mechanism of β-Lg with rNGO, drug loading and release on nanocomposite (rNGO/β[email protected]) will be simulated and discussed by DFT method based on M06-2×/aug-cc-pVDZ-PP calculations. The calculation results show that β-Lg reacts on the rNGO surface by forming a π-π bond. The adsorption energy (Eads = −25.99 kcal.mol-1) and the calculated thermodynamic functions indicate a favorable interaction between them, which causes the formation of rNGO/β-Lg nanocomposite at ambient temperature. By encapsulating the drug by nanocomposite, the softness of the chemical structure of the drug and its reactivity have decreased and the synthetic stability has increased. The value of charge transfer (ΔNmax = −0.16)) calculated for rNGO/β[email protected] indicates the transfer of electrons from the drug to the nanocomposite and the creation of stereo electronic resonance, hardening and stabilization of their geometric structure. It reduces the release rate of the drug and reduces its accumulation and toxicity in the body.

Facile synthesis of SnO2– CuSe nanocomposites with enhanced visible light photocatalytic performance

Wastewater treatment is currently one of the key topics addressing environmental-related challenges for the betterment of our lives. We report a comparative study on the photocatalytic properties of SnO2–CuSe nanocomposites with varying amounts of CuSe. The samples were prepared by simple and cost-effective hydrothermal and chemical methods. X-ray diffraction (XRD), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDAX) analysis confirmed the successful fabrication of the samples without any impurities. The average crystallite sizes were respectively determined to be around 23 and 26 nm for SnO2 and CuSe respectively. For the SnO2–CuSe nanocomposites, the crystallite sizes were calculated to be in the range of 20–28 nm. Field emission scanning electron microscopy (FE-SEM) images revealed a flower-like morphology for the SnO2, whilst the shape of pure CuSe is found to be of irregular plates. Similarly, the SnO2–CuSe nanocomposites exhibited coexisting flower-plates-like morphology dependent on the CuSe content. Electron Resonance Spectroscopy (ESR) also revealed paramagnetic defects in the prepared samples. UV–visible absorption measurements showed a red shift in the bandgap energy with increasing the CuSe content in the nanocomposite samples. The photocatalytic performance of the fabricated samples was determined by taking Rhodamine B (RhB) as a model dye. The nanocomposite sample with the composition of SnO2-32% CuSe showed the best photocatalytic performance. The Langmuir-Hinshelwood model was applied to determine the apparent rate constants.

Mechanical properties and micro mechanism of alkali-activated tannery sludge/fly ash composite cement-based recycled concrete

In order to alleviate the environmental degradation and resource waste caused by cement production and construction waste disposal, some cement is replaced by tannery sludge and fly ash, and natural aggregate is replaced by recycled coarse aggregate. The preparation of alkali activated tannery sludge/fly ash composite cement-based recycled concrete (AA-SFRC) is of great significance for the safe disposal and utilization of solid waste. In order to study the mechanism of the effect of alkali-activator on the mechanical properties and microstructure of AA-SFRC, six kinds of AA-SFRC with different alkali equivalents (AE) were designed, and the strength tests, nuclear magnetic resonance (NMR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were carried out. On this basis, the influence of AA-SFRC pore structure parameters on strength performance was discussed by using grey entropy analysis method, and a grey model GM (1, 5) prediction model of 28d strength was established. The results demonstrated that with the increase of AE, the AA-SFRC strength increased at first and then decreased, and the tension–compression ratio (Ts/Cs) remained in the normal range, between 0.065 and 0.081. When the AE was 9%, the mineral composition of AA-SFRC reached equilibrium, and the hydration reaction was the most sufficient. The compressive strength and splitting tensile strength reached the maximum. Meanwhile, the pore structure showed that the porosity and the proportion of macro pores were the smallest. The 28d strength of AA-SFRC was greatly affected by its 7d strength, first peak ratio, fractal dimension Dmax and porosity. The average relative errors between the predicted value of GM (1, 5) model and the experimental value were less than 0.03%. This study can provide a reference for the resource utilization of tannery sludge, fly ash and construction waste.

Investigation of silver-doped binary glass through modified Stöber process under surfactant

A native glass nanoparticle composition based on a binary system, “BGNPs,” was synthesized by a modified Stöber process under surfactant. Afterward, the glass was doped with silver (Ag), and their acellular bioactivity was studied. The synthesized bioactive glasses were characterized by thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmet–Teller (BET) and Barrett–Joyner–Halenda (BJH), X-Ray diffraction (XRD), nuclear magnetic resonance (NMR) and Scanning Electron Microscope attached with Energy-dispersive X-ray spectroscopy (SEM-EDS). Further, biological properties were analyzed before and after in-vitro tests by soaking the as-prepared bioglass nanoparticles in simulated body fluid (SBF) for different periods. Apatite layers covered the surface of the prepared nanoparticles, indicating their bioactivity from SEM images. Also, the pore size distribution of nano-spheroids particle sizes was within the range of 2–5 nm, and quantitative results from the EDS confirmed the Ag-doped in BGNPs, and both SEM and XRD spectra validated the above results. Using silver-doped prepared glasses, promising results were obtained regarding apatite formation.

Effects of dietary canthaxanthin on ultraviolet radiation stress in prawn Artemesia longinaris

The aims of this research were to investigate the effects of diets with added synthetic canthaxanthin (10% parafarm) and to evaluate its possible protective role under ultraviolet radiation (UVR) in prawn Artemesia longinaris. Three isoproteic and isolipidic diets (41% protein and 12% lipid) containing 0 (C0), 100 (C100), and 300 (C300) mg of canthaxanthin kg-1 of diet were prepared. Before initiating the radiation experiment, prawns were fed with the different diets for a period of 21 d in order to determine a possible accumulation of carotenoids. Afterwards, animals were exposed to two radiation treatments for 7 d: a) photosynthetically active radiation (PAR, 400-700 nm), and b) total radiation (PAR+UVR, 280-700 nm), under controlled conditions (19 ± 2 °C, salinity = 33, pH = 7). In animals exposed to PAR+UVR treatment, survival varied between 50 and 83.33% with the highest value in animals fed diet C300. At the end of the experiment, significant statistical differences were registered in integument carotenoid concentration. Under UVR stress, the highest decrease in non-polar carotenoid and esterified astaxanthin were recorded in prawns fed diets containing canthaxanthin. Scavenging properties were evaluated by electron resonance spectroscopy (EPR) using the stable 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical. Prawns fed with C300 showed the greatest activity to quench DPPH. Results suggested that dietary canthaxanthin could be acting as an antioxidant against reactive oxygen species and produced high tolerance under UVR stress.