Ascorbic Acid In Aqueous Solution Research Articles

Reduction of graphene oxide/alginate composite hydrogels for enhanced adsorption of hydrophobic compounds

Carbon-based materials, consisting of graphene oxide (GO) or reduced GO (rGO), possess unique abilities to interact with various molecules. In particular, rGO materials hold great promise for adsorption and delivery applications of hydrophobic molecules. However, conventional production and/or usage of rGO in aqueous solution often causes severe aggregation due to its low water solubility and thus difficulties in handling and applications. In our study, to prevent the severe aggregation of GO during reduction and to achieve a high adsorption capacity with hydrophobic compounds, GO/alginate composite hydrogels were first prepared and then reduced in an aqueous ascorbic acid solution at 37 °C. Adsorption studies with a model hydrophobic substance, rhodamine B, revealed that the reduced composite hydrogels are more highly absorbent than the unreduced hydrogels. In addition, the adsorption properties of the composite hydrogels, which are consequences of hydrophobic and ionic interactions, could be modulated by controlling the degree of reduction for the adsorption of different molecules. The composite hydrogels embedding rGO can be very useful in applications related to drug delivery, waste treatment, and biosensing.

Effects of radical scavengers on aqueous solutions exposed to heavy-ion irradiation using the liquid microjet technique

The effects of the radical scavenger ascorbic acid on water radiolysis are studied by fast heavy-ion irradiation of aqueous solutions of ascorbic acid, using the liquid microjet technique under vacuum. To understand the reaction mechanisms of hydroxyl radicals in aqueous solutions, we directly measure secondary ions emitted from solutions with different ascorbic acid concentrations. The yield of hydronium secondary ions is strongly influenced by the reaction between ascorbic acid and hydroxyl radicals. From analysis using a simple model considering chemical equilibria, we determine that the upper concentration limit of ascorbic acid with a radical scavenger effect is approximately 70μM.

Synthesis of cuprous oxide with morphological evolution from truncated octahedral to spherical structures and their size and shape-dependent photocatalytic activities

In this study, a facile room-temperature solution-chemical route has been developed to synthesize Cu2O crystals with various sizes and morphologies. Adjustment of feeding speed of the aqueous mixture of polyvinyl pyrrolidone (PVP) and ascorbic acid (AA) enables the Cu2O crystal morphology and size evolution. It is also interesting to find that, simple alteration of the feeding speed of AA aqueous solution enables the size of Cu2O crystals evolved, while the morphology of Cu2O crystals keep unchanged. These Cu2O crystals samples were used as photocatalysts for the decomposition of methyl orange (MO) under visible light irradiation. The results show that Cu2O spiny spheres with hierarchical structure exhibited superior photocatalytic activity compared with truncated octahedrons and spheres. In addition, the photocatalytic activity of truncated octahedral Cu2O can be greatly improved by decreasing the size of Cu2O particles. The work demonstrated a novel strategy for the shape and size-controlled synthesis of Cu2O crystals with superior photocatalytic activities.

Ascorbic acid microencapsulation by spray chilling: Production and characterization

This study reports on the use of spray chilling to synthesize solid lipid microparticles containing ascorbic acid and describes the characterization of the resulting microparticles. Lauric acid (LA)/oleic acid (OA) mixtures at 70/30, 80/20, and 90/10 g:g ratios served as carrier. Different carrier/core (core = aqueous ascorbic acid solution 30 g/100 g) ratios, namely 70/30, 75/25, and 80/20 (g:g), were tested. The synthesized microparticles presented high TE values, which varied from 89% to 98%; differences between experiments were not significant (p > 0.05). EE values were inversely proportional to the amount of LA in the carrier; EE ranged from 58% to 88%. The mean volume moment of particle D[4,3] of the microparticles containing LA concentrations of 70 g/100 g of lipid and 90 g/100 g of lipid ranged from 45 to 67 μm and from 18 to 24 μm, respectively. The core release profile revealed that microparticles containing intermediate concentration of LA in the carrier (80 g/100 g of lipid) retained the ascorbic acid core better. The ratio between the fatty acids used as carrier rather than the ratio between the carrier and the core affected the characteristics of the microparticles the most.

Active bilayer films of thermoplastic starch and polycaprolactone obtained by compression molding

Bilayer films consisting of one layer of PCL with either one of thermoplastic starch (S) or one of thermoplastic starch with 5% PCL (S95) were obtained by compression molding. Before compression, aqueous solutions of ascorbic acid or potassium sorbate were sprayed onto the S or S95 layers in order to plasticize them and favor layer adhesion. S95 films formed bilayers with PCL with very good adhesion and good mechanical performance, especially when potassium sorbate was added at the interface. All bilayers enhanced their barrier properties to water vapour (up to 96% compared to net starch films) and oxygen (up to 99% compared to PCL pure). Bilayers consisting of PCL and starch containing 5% PCL, with potassium sorbate at the interface, showed the best mechanical and barrier properties and interfacial adhesion while having active properties, associated with the antimicrobial action of potassium sorbate.

Redox-Induced Reversible Uptake–Release of Cations in Porous Ionic Crystals Based on Polyoxometalate: Cooperative Migration of Electrons with Alkali Metal Ions

Redox-active porous ionic crystals based on polyoxometalates (POM) were synthesized. By treating the crystal with an aqueous solution of ascorbic acid (reducing reagent) and KCl, one-electron reduction of POM proceeded followed by simultaneous uptake of K+. Interestingly, the reduction did not proceed without KCl, and the molecular size of ascorbic acid was too large to enter the porous crystal lattice. The time courses of reduction and K+ uptake were monitored by UV–vis spectroscopy and atomic absorption spectrometry (AAS), respectively. Both profiles could be reproduced by the linear driving force (LDF) model with similar rate constants. The reduced crystal could be oxidized with aqueous chlorine solution followed by the release of K+, and the redox cycles were reversible. The water sorption properties of the crystals could be controlled by the types of alkali metal ions incorporated. The Cs+ uptake and the simultaneous reduction of the crystal proceeded much faster than in the case of K+, which is in line with the trends in the Gibbs energies of hydration of alkali metal ions. Complete selectivity to Cs+ was observed in the uptake of ions from an aqueous binary mixture of Cs+ and Na+. All these results suggest the cooperative migration of electrons with alkali metal ions and the redox induced ion-exchange in porous ionic crystals based on POM.

Ascorbic acid attenuates acute pulmonary oxidative stress and inflammation caused by zinc oxide nanoparticles.

It is known that inhalation of zinc oxide nanoparticles (ZnO NPs) induces acute pulmonary dysfunction, including oxidative stress, inflammation, and injury, but there are no reports on how to prevent these adverse effects. We have previously reported that the pulmonary symptoms caused by ZnO NPs were associated with oxidative stress; in the present study, we therefore investigated the use of ascorbic acid (AA), which is known as vitamin C, to prevent these toxic effects. A ZnO NP dispersion was introduced into rat lungs by intratracheal injection, and thereafter a 1% aqueous AA solution was given as drinking water. Bronchoalveolar lavage fluid was collected at 1 day and 1 week after injection, and lactate dehydrogenase (LDH) activity, heme oxygenase-1 (HO-1), and interleukin-6 (IL-6) levels were measured. In addition, expression of the chemokine cytokine-induced neutrophil chemoattractants (CINCs), HO-1, and metallothionein-1 (MT-1) genes in the lungs were determined. Acute oxidative stress induced by ZnO NPs was suppressed by supplying AA. Increases in LDH activity and IL-6 concentration were also suppressed by AA, as was the expression of the CINC-1, CINC-3, and HO-1 genes. Oral intake of AA prevents acute pulmonary oxidative stress and inflammation caused by ZnO NPs. Intake of AA after unanticipated exposure to ZnO NPs is possibly the first effective treatment for the acute pulmonary dysfunction they cause.

Green synthesis and formation mechanism of nanostructured Bi2Te3 using ascorbic acid in aqueous solution

Nanostructured Bi2Te3 can be synthesized in 100% yield by a chemical reduction method in aqueous TeO32− solution using mild and safe ascorbic acid as reducing agent instead of toxic reducing agent commonly employed. Additionally, ascorbic acid works not only as reducing agent but also as capping agent which has an excellent oxidation resistance. In general, ascorbic acid cannot directly reduce TeO32− to metal Te due to the lower reduction potential of TeO32−. Electrochemical analysis and ESI-TOFMS study showed that TeO32− changes to metal Te via easily reducible Te species with ascorbic acid [TeO2(C6H6O6)]2−, and subsequently metal Te triggers the reduction of Bi species, resulting in the Bi2Te3 nanoparticles. This finding creates a path of green synthesis method for nanostructured metal tellurides which have various applications.

Effect of DBU (1,8-Diazobicyclo[5.4.0]undec-7-ene) Based Protic Ionic Liquid on the Volumetric and Ultrasonic Properties of Ascorbic Acid in Aqueous Solution

In order to understand the strength and type of interactions involved in ternary solutions, the effect of solute or cosolute concentration and temperature is needed, as an understanding of these interactions is helpful in biochemical and biophysical chemistry. In this regard, we have studied the volumetric and ultrasonic properties of one of the most important vitamins, i.e., ascorbic acid, in water and in the presence of newly synthesized protic ionic liquid (1,8-diazabicyclo[5.4.0]undec-7-en-8-ium trifluoroacetate) at temperatures of 293.15–328.15 K and at atmospheric pressure. The experimentally measured density and speed of sound data were used to calculate apparent molar volume and isentropic compressibility, infinite dilution partial molar volume, and partial molar isentropic compressibility. Volume of transfer (ΔtV2° and ΔtK°s,2), expansion coefficients, pair and triplet volumetric interaction coefficients were also evaluated and discussed in terms of various interactions occurring between ascorbic...

Photochemical formation and photoelectrochemical properties of TiO2/Sb2S3 heterostructures

Abstract The photocatalytic deposition of antimony(III) sulfide on the surface of TiO 2 films on the conductive FTO glass was investigated. The photoprocess yields particles of amorphous and almost stoichiometric Sb 2 S 3 with a size of 150–300 nm and spherical micrometer particles enriched with Sb with a Sb:S ratio that decreases gradually from 13:1 in the particle center to 5:1 at the surface. Thermal treatment of the FTO/TiO 2 /Sb 2 S 3 films at 350 °C results in the transformation of amorphous antimony(III) sulfide into crystalline stibnite without extensive changes in the film morphology. The crystalline FTO/TiO 2 /Sb 2 S 3 films exhibit photoelectrochemical activity when illuminated in the spectral range of λ > 350 nm in aqueous solutions of ascorbic acid as a sacrificial electron donor. The maximal photocurrent density generated by the TiO 2 /Sb 2 S 3 heterostructure is higher than the photoresponse of the starting FTO/TiO 2 film by a factor of 3.6. Deposition of an intermediary layer of In x (OH) y S z on the interface between TiO 2 and Sb 2 S 3 results in a further 3-fold increase in the photoelectrochemical activity of the FTO/TiO 2 /Sb 2 S 3 heterostructure.

A facile fabrication of platinum nanoparticle-modified graphite pencil electrode for highly sensitive detection of hydrogen peroxide

A novel platinum nanoparticle-modified graphite pencil electrode (PtNP-GPE) for a non-enzymatic determination of H2O2 is proposed. The PtNP-GPE is prepared by heating a GPE in an aqueous solution of ammonium tetrachloroplatinate(II) and ascorbic acid at 75°C for 15min. Both unmodified and PtNP-GPE are characterized using field-emission-SEM and cyclic voltammetry. The PtNP-GPE showed better electrocatalytic properties toward the electrochemical redox reaction of H2O2 than that of the unmodified GPE. The PtNP-GPE amperometric response is tested at four different potentials (+0.7, +0.5, −0.2 and −0.3V vs. Ag/AgCl reference electrode). Taking into consideration both the intensity of the amperometric response and detector stability, the applied potential of +0.5V is the best among the tested potentials. The PtNP-GPE amperometric response of H2O2 at +0.5V is linear from 10 to 110μM (R2=0.999) with a detection limit of 3.6μM.

Effects of solution spraying during hot air drying on drying rate, surface hardening and browning of fresh-cut Japanese pear

Three types of solutions (distilled water, aqueous ascorbic acid solution and aqueous citric acid solution) were sprayed periodically on the surface of fresh-cut Japanese pear during hot air drying at 40, 50 and 60 °C. The effects of solution spraying on the drying kinetics, the surface hardening, and the sample discoloration were investigated. The drying rates of the sprayed samples increased 58–63, 16–19 and 20–22% in comparison with those of the non-sprayed samples at 40, 50 and 60 °C, respectively. The hardness of the sprayed samples decreased 12–24% and 2–9% compared to that of the non-sprayed samples, and the total color difference (ΔE) was 27–44 and 20–33% less compared the non-sprayed samples at 40 and 50 °C, respectively.

Poly(vinyl alcohol) gate dielectric surface treatment with vitamin C for poly(3-hexylthiophene-2,5-diyl) based field effect transistors performance improvement

We report on organic field effect transistors (OFETs) prepared using cross-linked poly(vinyl alcohol) (cr-PVA) as gate dielectric and 100% regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) as channel semiconductor. The gate dielectric surface was treated using an environmentally friendly aqueous solution of ascorbic acid (vitamin C), which is a reducing agent. The treatment contributed to the passivation of positively charged defects present on the surface of cr-PVA gate dielectric, hence resulting in the enhancement of capacitance, field effect mobility, ON/OFF current ratio and sub-threshold swing.

Synthesis of Monodisperse, Quasi-Spherical Silver Nanoparticles with Sizes Defined by the Nature of Silver Precursors

Monodisperse, quasi-spherical silver nanoparticles (Ag NPs) with controlled sizes have been produced directly in water via adding the aqueous solutions of the mixtures of AgNO3 and sodium citrate to boiling aqueous solutions of ascorbic acid (AA). Different compounds, including NaCl, NaBr, KI, Na2SO4, Na2CO3, Na2S, and Na3PO4, are added to the AgNO3/citrate mixture solutions to form new silver compounds with fairly low solubility in water, which are used as precursors instead of soluble Ag(+) ions to synthesize Ag NPs via AA/citrate reduction. This enables us not only to produce monodisperse, quasi-spherical Ag NPs but also to tune the sizes of the resulting NPs from 16 to 30 nm according to the potential of new silver precursors as well as the concentrations of anions.

A theoretical study on ascorbic acid dissociation in water clusters

Dissociation of ascorbic acid in water has been studied by using a cluster model. It was examined by density functional theory (DFT) with the В3LYP, M06, and wB97XD functionals and a 6-311++G(d,p) basis set. The thermodynamic and kinetic characteristics of proton transfer from ascorbic acid molecule to water clusters were calculated as well as the equilibrium constants (pK a ) for the related processes. The used functionals in the DFT method together with continuum solvent models provided results close to the experimental data for the dissociation constant of ascorbic acid in aqueous solution.

Kinetics of the Rapid Reaction between Iodine and Ascorbic Acid in Aqueous Solution Using UV–Visible Absorbance and Titration by an Iodine Clock

An iodine clock is the basis for studying the kinetics of the fast reaction between iodine and ascorbic acid in aqueous solution. UV–visible absorbance, where the molar absorptivity of the triiodide ion is high, is equated with the total concentration of iodine, through the equilibrium, I2 + I– ⇌ I3–, established when the iodine clock is concluding its steady-state titration of ascorbic acid. Persulfate ion is the primary oxidant catalyzed by the iodide ion, which produces the iodine titrant and is recycled. A method testing the second-order rate equation, R1 = k[iodine][ascorbic acid], uses the coefficient of variation, CV. This locates equivalence, enabling [ascorbic acid] to be measured and contributes to a procedure where rate of reaction, R1, at different concentrations of iodine and ascorbic acid determines an average value of the overall rate constant, k. In combination with results from another source, the rate constants of the two individual forms of iodine reacting with ascorbic acid also are de...

Electrocatalytic Activity of Carbonized Nanostructured Polyanilines for Oxidation Reactions: Sensing of Nitrite Ions and Ascorbic Acid

A comparative study of the electrocatalytic activity of nitrogen-containing carbon nanomaterials, prepared by the carbonization of nanostructured polyaniline (PANI) salts, for the electrooxidation reactions is presented. Nanostructured PANI salts were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 5-sulfosalicylic acid (PANI-SSA), 3,5-dinitrosalicylic acid (PANI-DNSA) as well as without added acid (PANI), and subsequently carbonized to c-PANI-SSA, c-PANI-DNSA and c-PANI, respectively. Glassy carbon tip was modified with nanostructured c-PANIs and used for the investigation of sensing of nitrite and ascorbic acid in aqueous solutions as model analytes by linear sweep voltammetry. All three types of the investigated c-PANIs gave excellent response to the nitrite ions and ascorbic acid electrooxidation. The lowest peak potential for nitrite ion oxidation exhibited c-PANI (+0.87V vs. SCE), and for ascorbic acid oxidation both c-PANI and c-PANI-SSA (ca.+0.13V vs. SCE). Electrochemical data were correlated with structural and textural data obtained by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental and nitrogen sorption analysis.

Spectrophotometric Determination of Ascorbic acid in Aqueous Solutions and in Pharmaceuticals formulations

A new sensitive colorimetric method for determination of ascorbic acid tablet in aqueous solution. The method is based on the formation of colored azo dye by diazotization of 2, 4dichloroaniline followed by azo-coupling reaction between the resulting product and ascorbic acid. The optimum conditions that gave maximum absorption of azo dye at535nm, with best concentration of reactant and order of addition were studied to get the highest sensitivity (e=2315) L.mol -1 .cm -1 with a wide range of calibration curves (2-70) µg/ml good repeatability (RSD% 0.68 and 1.49), the recovery (99.56 - 100.30)%, Erel% (-0.20 and 0.44) were gave , Pharmaceutically prepared tablets were measured with the new technique using standard addition method given a very good recovery % (101.25 and 98.77) with a small Erel% (-1.25 and 1.23).

A new voltammetric sensor for electrocatalytic determination of vitamin C in fruit juices and fresh vegetable juice using modified multi-wall carbon nanotubes paste electrode

The electrocatalytic oxidation of ascorbic acid (AA) has been studied by p-aminophenol modified carbon nanotubes paste electrode (APMCNTPE). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the suitability of AP as a mediator for the electrocatalytic oxidation of AA in aqueous solution. The oxidation of AA occurs at a potential about 320 mV less positive than with the unmodified carbon paste electrode at pH 7.0. The catalytic reaction rate constant, kh was calculated (2.257 × 103 M−1s−1) using chronoamperometry. The differential pulsevoltammetric (DPV) peak currents of the electrode increased linearly with the corresponding AA concentration in the range of 2.0 × 10−7 M – 1.2 × 10−4 M with a detection limit of 8.0 × 10−8 M. The influence of pH and potential interfering substances on the determination of AA were studied. Finally, the proposed method was also examined as a selective, simple and precise electrochemical sensor for the determination of AA in real samples such as fruit juices and fresh vegetable juice.

Simple Synthesis of Monodisperse, Quasi-spherical, Citrate-Stabilized Silver Nanocrystals in Water

Monodisperse, quasi-spherical silver nanocrystals (Ag NCs) have been produced directly in water via adding the aqueous solution of a mixture of AgNO3, sodium citrate, and KI into the boiling aqueous solutions of ascorbic acid (AA). The AA is used to significantly accelerate reduction of AgNO3 in order to promote a very fast nucleation, and the KI is used to tailor the growth of the Ag NCs into a quasi-spherical shape via its preferential adsorption on the NC {111} facets. The major role of citrate is to stabilize the newly formed NCs, whereas it has a minor contribution to reduction of AgNO3. The synergy of the effects of AA, citrate, and KI can significantly narrow the size distributions of the Ag NCs obtained so and transform the NC shapes to be truly quasi-spherical.