Aqueous Solution Of Citric Acid Research Articles

Complex formation of indium(iii) with citric acid in aqueous solution

Complex formation of In3+ ion with citric acid in an aqueous solution was studied by pH-metric titration at the molar ratio of the reactants [In3+] : [H4Cit] = 1 : 1, 1 : 2, and 1 : 3 in a range of pH 2—10. The mathematical simulation of equilibria in an indium(iii)—citric acid system was performed using the CPESSP program package. The formation of 1 : 1, 1 : 2, and 1 : 3 indium(iii) citrate complexes with different degrees of nuclearity and protonation was established. The equilibrium constants of formation of the complexes were calculated. The predomination of the polynuclear indium(iii) citrate complexes at the equimolar metal to ligand ratio of was observed in almost the whole pH range studied (3—10).

Migration of heavy metals from recycled polyethylene terephthalate during storage and microwave heating

Agencies such as the Environmental Protection Agency and Agency for Toxic Substances and Disease Registry are pushing for increased use of recycled polyethylene terephthalate. Packaging materials made from recycled polyethylene terephthalate are used for direct food contact in recycled rigid containers and films. Most recycled polyethylene terephthalate packaging materials contain heavy metal catalysts, the most common being antimony. The recycling process has the potential to increase degradation products, chemical additives and polymerization side-products. Recent studies using inductively coupled plasma-atomic emission spectrometry confirmed the presence of cadmium, chromium, lead, nickel and antimony in food packaging. These heavy metals have the potential to migrate onto and into food products, and limited governmental regulation of these contaminants in recycled polyethylene terephthalate packaging materials increases public health risks. In this study, 22 samples of known heavy metal content were tested for heavy metal migration of lead, cadmium, chromium, nickel and antimony into a 5% aqueous citric acid solution or deionized water. Samples were exposed for 5 min to microwaves from a 1700 W microwave oven set to 70% power, or were stored at 7.2 or 22.2℃ for 1, 7 or 14 days before testing. The samples were analyzed for heavy metal content per ASTM E1613-04, the standard test method for the determination of lead by inductively coupled plasma-atomic emission spectrometry. Neither the storage nor the microwave treatments had a significant effect on heavy metal migration, while exposure to 5% aqueous citric acid resulted in a higher rate of heavy metal leaching from the recycled polyethylene terephthalate compared to samples exposed to deionized water. A very low percentage of the samples tested had heavy metals migrate above detectable levels indicating that most recycled polyethylene terephthalate packaging materials are relatively safe for direct food contact.

ChemInform Abstract: High‐Voltage Cathode Materials for Lithium‐Ion Batteries: Freeze‐Dried LiMn0.8Fe0.1M0.1PO4/C (M: Fe, Co, Ni, Cu) Nanocomposites.

AbstractLiMn0.8Fe0.1M0.1PO4/C (M: Fe, Co, Ni, Cu) nanocomposite cathode materials are prepared by freeze‐drying of aqueous solutions of citric acid, Mn(OAc)3, LiOH, NH4H2PO4, and M(OAc)2 in stoichiometric quantities (‐80 °C, 48 h, 3 x 10‐1 mbar).

Green Electrospinning and Crosslinking of Polyvinyl Alcohol/Citric Acid

The present study reports green electrospinning of polyvinyl alcohol (PVA) / citric acid nanofiber membranes, and the membranes were then crosslinked by heat treatment. The electric conductivity of the PVA aqueous solution increases rapidly and the growth slows down along with the increase of citric acid content. The viscosity of 13 wt% PVA aqueous solutions with citric acid had a small increase and remained stable in one week, which was suitable for electrospinning fibers. Porous, interconnected nonwoven nanofiber membranes were electrospun from a thoroughly mixing of PVA/ citric acid aqueous solution. The membranes were then heat treated at 140 °C for 2 h. The postelectrospinning crosslinked nanofiber membranes were insoluble in water, while the non-crosslinked electrospun nanofiber membranes dissolved instantaneously. FT-IR spectrum, X-ray diffraction, and DSC thermograms reveal that crosslinking of PVA nanofiber membranes occurred through esterfication reaction during heat treatment.

Blends of Epoxidized Alkyd Resins Based on Jatropha Oil and the Epoxidized Oil Cured with Aqueous Citric Acid Solution: A Green Technology Approach

Alkyd resins with 100% phthalic anhydride were prepared from jatropha oil by two-stage alcoholysis–polyesterification reactions. To improve the performance characteristics, resins were blended with different wt % of epoxidized jatropha oil (EJO) and aqueous citric acid solution without the addition of any other catalyst or solvent. Blending was facilitated via epoxidation of the alkyd resins. The prepared blends were characterized by Fourier transform infrared and NMR (1H and 13C) spectroscopy studies. It was observed that the properties like curing time, chemical resistance, scratch hardness, thermal stability, and tensile strength of the alkyd resins improved significantly on blending. With 50 wt % EJO content, the thermal stability and tensile strength of the blends increased by 42 °C and 3.18 MPa, respectively. The results indicate the strong influence of the amount of EJO and citric acid on the performance of the alkyd resins. The thermal and mechanical properties of the cured films can be further im...

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.

Pulse electrodeposition of Pt and Pt–Ru methanol-oxidation nanocatalysts onto carbon nanotubes in citric acid aqueous solutions

Abstract In this study, platinum nanoparticle/carbon nanotube (Pt NP/CNT) and platinum–ruthenium nanoparticle (Pt–Ru NP/CNT) hybrid nanocatalysts were prepared by the pulse-electrodeposition method in different aqueous solutions containing citric acid (CA) or sulfuric acid (SA). The electrocatalytic properties of the Pt NP/CNT and Pt–Ru NP/CNT electrodes prepared using different aqueous solutions were investigated for methanol oxidation. The results show that the electrochemical mass activities of these hybrid nanocatalysts prepared in the CA aqueous solution were increased by factors of 1.46 and 2.77 for Pt NPs and Pt–Ru NPs, respectively, compared with those prepared in SA aqueous solutions using the same procedure. These increased mass activities are attributed to the CA playing dual roles as both a stabilizing agent and a particle size reducing agent in the aqueous solutions. The approach developed in this work enables further reductions in the particle sizes of noble-metal nanocatalysts.

Green and simple route toward boron doped carbon dots with significantly enhanced non-linear optical properties

Microwave heating of an aqueous solution of citric acid, boric acid and urea affords boron-doped carbon dots (C-dots) with ultrafine size (2–6nm) and quasi-spherical shape. The new dots are freely dispersible in water providing stable, optically transparent dispersions with olive-green color. The optical properties of the dots were studied in respect to their photoluminescence and nonlinear optical response. Boron-doped C-dots exhibit absorption–emission features that strongly resemble the optical properties of conventional quantum dots with a strong blue fluorescence under UV excitation. Importantly, we demonstrate for the first time that boron doping in C-dots causes a significant enhancement of the nonlinear optical response compared to un-doped carbon dots. This result is in line with previous studies reporting a similar effect on the non-linear optical properties of boron-doped silicon nanocrystals.

Germanium oxide removal by citric acid and thiol passivation from citric acid-terminated Ge(100).

Many applications of germanium (Ge) are underpinned by effective oxide removal and surface passivation. This important surface treatment step often requires H-X (X = Cl, Br, I) or HF etchants. Here, we show that aqueous citric acid solutions are effective in the removal of GeOx. The stability of citric acid-treated Ge(100) is compared to HF and HCl treated surfaces and analyzed by X-ray photoelectron spectroscopy. Further Ge surface passivation was investigated by thiolation using alkane monothiols and dithiols. The organic passivation layers show good stability with no oxide regrowth observed after 3 days of ambient exposure.

ChemInform Abstract: Controllable Growth of SnS2/SnO2 Heterostructured Nanoplates via a Hydrothermal‐Assisted Self‐Hydrolysis Process and their Visible‐Light‐Driven Photocatalytic Reduction of Cr(VI).

AbstractA series of SnS2/SnO2 heterostructured nanoplates with different SnO2 contents are synthesized by self‐hydrolysis of SnS2 nanoplates (obtained from aqueous mixtures of SnCl4 and thiourea, autoclave, 180 °C, 10 h) in the presence of an aqueous citric acid solution (autoclave, 180 °C, 2—24 h).

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phase), and citric acid aqueous solutions (feed phase). Two factorial designs (2 5–1 and 2 3 ) were used to define suitable operating conditions, in a single stage, producing citric acid solutions at 0.25 g mL –1 from aqueous feed solutions at 0.10 g mL –1 . The parameters investigated and the best operating conditions obtained were pH of the feed phase (pH = 1.5), surfactant (w s = 2 %) and carrier concentrations in the membrane phase (w c = 20 %), stirring speed (v = 145 rpm), and permeation time (t = 10 minutes) and the response variables were the citric acid concentration in the inner and feed phases and inner phase swelling. Under these conditions, an extraction greater than 50 % and swelling equal to 80 % were obtained. Use of recycled membranes as well as extraction in multiple stages was also evaluated. Experiments of recycling revealed that the membranes can be reused for at least three times with good performance. Extraction in multiple stages showed high efficiency for the citric acid separation (~100 %) after three steps of operation.

Induction coil heater prepared highly fluorescent carbon dots as invisible ink and explosive sensor

We report a new and facile method for the synthesis of highly fluorescent carbon dots (Cdots) using a commercially available induction coil heater. An aqueous solution of citric acid and a diamine compound was heated at 100 °C for 12–15 min, upon which the Cdots were produced. The Cdots, with an average size of less than 5 nm (produced when ethylenediamine was used), emitted a blue light with a high quantum yield when excited under UV light. The quantum yield was dependent on the nature of diamine and was as high as 73.5% for ethylenediamine. The as-prepared Cdots could be easily converted into a gel by mixing with chitosan biopolymer. The gel could be used for filling up the refill of a ball-point pen and can be used for UV-active marking, for sensing of explosive compounds (such as picric acid and 2,4-dinitrophenol) with high efficiency and for other fluorescence based applications. The use of a commercial induction coil heater, scalability and high chance of commercial viability make the method particularly appealing.

X-ray analysis and optical properties of nickel oxide thin films

Nanoparticles of NiO were prepared by a homogeneous precipitation method with an aqueous solution of nickel nitrate hexahydrate and citric acid. The microstructure and surface morphology of NiO powder were characterized by thermogravimetric (TGA) analysis, differential scanning calorimeter (DSC), X-ray diffraction (XRD), and infrared (IR) spectroscopy. Different thicknesses of nickel oxide (NiO) thin films were deposited onto highly cleaned glass substrates by the electron beam technique. Their structural characteristics were studied by X-ray diffraction (XRD) and scan electron microscope (SEM). The XRD investigation shows that NiO films are polycrystalline with an cubic type structure. The microstructure parameters, e.g., crystallite size and microstrain were calculated. The optical constants (n, k) and film thicknesses of NiO thin films were obtained by fitting the ellipsometric parameters (ψ and Δ) data using three layer model systems in the wavelength range 300–1100nm. It is found that the refractive index, n increases with the increase of the film thickness. The possible optical transition in these films is found to be allowed direct transitions. The direct energy gaps increase with increasing of the film thickness.

One-Dimensional Structure Comprising Oriented Na3V2(PO4)3 Nanoparticles in a Carbon Sheath for a Na Cathode Material

IntroductionDevelopment of Na-ion batteries is desired as alternative energy storage devices to Li-ion batteries. NASICON frameworks (Na3M2(XO4)3; X = Si4+, P5+, S6+, Mo6+, As5+) are suitable to Na-ion intercalation electrode materials due to pass for fast ion transport. In particular, Na3V2(PO4)3 is a promising candidate for cathode materials in Na-ion batteries, because Na3V2(PO4)3 exhibits relatively high redox potential of V3+/V4+ at 3.37 V (vs. Na/Na+) and moderate theoretical capacity of 117.6 mAh/g. However, low electronic conductivity and lattice volume change during sodiation/desodiation of Na3V2(PO4)3give rise to low performance about micrometer-scale particles that are often yielded through traditional solid-state reaction.Structural and morphological control can improve electrochemical properties of electrode materials. In the present study, we have designed mesostructure that consists of oriented Na3V2(PO4)3 nanoparticles in a carbon sheath, so as to meet the requirements as high-performance Na-ion electrode materials. The assembly comprising oriented nanoparticles possesses a short Na-ion transport pass and effectively relieves the elastic strain during sodiation/desodiation. In addition, the carbon sheath surrounding nanoparticles supplies a sufficient electron conductive pass. These features enable the long cycle performance and high rate capability of the electrode.Experimental SectionThe typical procedure for preparation of Na3V2(PO4)3 nanowire with the mesostructure from electrospun precursor fiber is as follows: 0.15 mol·dm−3 NH4VO3 and stoichiometric amount of NH4H2PO4 and NaOH were added to 10 ml of citric acid aqueous solution (0.12 mol·dm−3). To dissolve the reagents, the aqueous solution was aged for 1 h at 90 ºC. After cooling at room temperature, 60 g·dm−3poly(acrylic acid) was dissolved into the solution. Precursor fiber obtained by electrospinning was heated at 800 ºC for 10 h in Ar flow condition.The resultant materials were observed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For crystal structural analysis, X-ray diffraction was measured with Cu Ka radiation in steps of 0.01° over the range from 10 to 80º. Thermogravimetric analysis was conducted up to 1000 °C in air flow condition. Raman spectroscopy was recorded to confirm existence of amorphous carbon.Electrochemical properties were measured in three electrode beaker cells. The resultant nanowire including amorphous carbon (85 wt%) were ground with further acetylene black (10 wt%) and polytetrafloroethylene (5 wt%) into a paste for electrochemical measurements. Sodium metal pressed on a SUS-304 mesh was used for counter and reference electrodes. 1M NaClO4propylene carbonate solution was used as electrolyte. The cutoff voltages were 3.8 V for charging (Na-ion extraction) and 2.5 V for discharging (Na-ion insertion). Specific current rate and capacity were calculated for only active materials.Results and DiscussionObtained compounds were confirmed with powder X-ray diffraction (XRD) measurement and the Rietveld refinement. The XRD pattern was refined by Na3V2(PO4)3. Morphology of the product was observed with scanning electron microscopy (SEM). Precursor fiber exhibited fibrous morphology, estimated to be 500 nm in diameter with SEM. Even after the heating treatment, nowoven fabric consisting of nanowires was observed, though the diameter is reduced to 200 nm.To confirm the formation of the mesostructure, transmission electron microscopy (TEM) obeservation was carried out. Figure 1a shows core-sheath structure in nanowires, where amorphous carbon sheath that is around 50 nm in thickness enfolds with aggregated nanoparticles 20-50 nm in size. Indeed, the Raman spectrum of the nanowires showed the broaden G-band and D-band of amorphous carbon around 1580 cm-1 and 1350 cm-1. The thermogravimetric curve of nanowire measured in air flow condition also suggested the existence of the carbon sheath, the amount of which in the product was estimated to be around 12 wt%. Selected-area electron diffraction (SAED) analysis of the nanowire shows an arched pattern, suggesting that nanoparticles in the carbon sheath are crystallographically oriented into the carbon sheath (Figure 1b).The electrochemical properties of the nanowire were evaluated by the charge-discharge experiments at various current rate (0.1, 0.2, 0.5, 1 and 2C rate). The charge-discharge curves show the flat plateau potential of the redox V4+/V3+ couple at 3.37 V vs. Na/Na+, which is in good agreement with previous studies. The core-sheath nanowire shows an initial discharge capacity of 109 mAh/g at 0.1 C rate (theoretically 117.6 mAh/g) (Figure 2) and the initial discharge capacity at 1C rate is 94 mAh/g (80% of the theoretical capacity). Comparing with electrochemical properties of bulk Na3V2(PO4)3 that were obtained by solid-state reaction, The core-sheath nanowire exhibited lager capacity. The designed structure enabled efficient charge-discharge reaction at moderate current rate.

Polymer-templated electrodeposition of Ag nanosheets assemblies array as reproducible surface-enhanced Raman scattering substrate.

Position-configurable, reproducible, vertically aligned nanosheets assemblies (ANAs) arrays are fabricated by polymer-templated electrodeposition method at room temperature. Here, nanoimprint lithography is utilized to fabricate polymer template on the fluorine-doped tin oxide substrate for the purpose of evenly tuning the location of Ag nanostructures. Subsequently, vertically aligned ANAs can be achieved at the bottom of each hole via electrodeposition in a mixed aqueous solution of AgNO3 and citric acid. To obtain uniform ANAs array, we have systematically investigated the factors that influenced the electrodeposition. It was found that the formation of uniform ANAs arrays is strongly depended on the seeding layer, citric acid concentration, electrodeposition potential and time. The as-synthesized ANAs array exhibited a remarkable SERS activity and Raman signal reproducibility to rhodamine 6G, a concentration down to 10(-13) M can be identified. Our results revealed that the ANAs array is a highly desirable candidate as the reliable enhancer for high performance SERS analysis.

Cu/Cu Direct Bonding by Metal Salt Generation Bonding Technique with Formic Acid and Citric Acid

The effect of formic acid and citric acid surface modification on the bonded strength of the solid-state direct bonded interface of copper was investigated by SEM observations of interfacial microstructures and fractured surfaces. Copper surfaces were modified by boiling in 98% formic acid for 0.6 ks and 17% aqueous solution of citric acid for 0.96 s. Solid-state bonding was performed in a vacuum chamber at bonding temperature of 423 ~ 673 K under a pressure of 588 N (bonding time of 0.9 ks). As a result of surface modification by formic acid and citric acid, bonded joints were obtained at a bonding temperature 150 K (formic acid) and 100 K (citric acid) lower than that required for non-modified surfaces, and the bond strength was comparable to that of the maximum load.

Chemical treatment of Cd 1 – x Mn x Te single crystals with H 2O2 –HI–citric acid aqueous solutions

Chemical treatment of Cd 1 – x Mn x Te single crystals with H 2O2 –HI–citric acid aqueous solutions

Preparation, Microstructural and Optical Characterization of NiO Nanoparticles

A fine NiO powders were prepared by a homogeneous precipitation method with an aqueous solution of nickel nitrate hexahydrate and citric acid. The microstructure, surface morphology of NiO were characterized b

ChemInform Abstract: Polar and Magnetic Layered A‐Site and Rock Salt B‐Site‐Ordered NaLnFeWO6 (Ln: La, Nd) Perovskites.

AbstractNaLaFeWO6 (I) and NaNdFeWO6 (II) are prepared by thermal decomposition (1% H2/Ar, 900 °C, 6 h for (I), 5% H2/N2, 850 °C, 2 h for (II)) of appropriate precursors obtained by reacting stoichiometric amounts of Na2CO3, La2O3, Nd2O3, FeC2O4, and (NH4)10W12O41 in aqueous citric acid solution containing HNO3 followed by solvent evaporation to yield an organic resin which is dried and decomposed (air, 600 °C, 12 h).

ChemInform Abstract: Investigation of the LiCo1‐xMgxPO4 (0 ≤ x ≤ 0.1) System.

AbstractThe title compounds are prepared by a sol—gel method from aqueous solutions of LiOAc, Co(OAc)2, Mg(OAc)2, citric acid, and phosphoric acid followed by annealing at 300 °C for 5 min in flowing air, and at 730 °C for 12 h in flowing nitrogen.