Sodium Borate Research Articles

Voltage program-based MEKC with LIF detection for rapid quantification of native capsaicin and dihydrocapsaicin in foods

Voltage program (VP)-based micellar electrokinetic chromatography (MEKC) with a laser-induced fluorescence (LIF) detector was developed for fast, high-sensitivity detection of native capsaicin (CAP) and dihydrocapsaicin (DHC) in various foods. The combination of mixed nonionic (Tween 20) and anionic (SDS) surfactants in a sodium borate running buffer showed excellent separation efficiency, selectivity, and speed without loss of resolving power (Rs > 2). Compared to conventional UV absorption, LIF showed enhanced detection sensitivity with detection limits at the pM level. In addition, the developed VP-based MEKC-LIF method was successfully applied for quantification of capsaicin in chili pepper, baechu, and kimchi at a 98% confidence level. CAP and DHC were also analyzed within a short time in extracts from real samples of gochujang, snacks (Swingchip®), black pepper, and ginger but were not detected in garlic.

Effect of Gamma Irradiation on Structural and Optical Properties of Zirconium Incorporated Sodium Borate Glasses

ABSTRACT The effects of gamma irradiation in the dose rate of 25 kGy on the structural and optical properties of ZrO2 doped sodium borate glasses were studied. Glassy nature confirmed by XRD and all the physical parameters were calculated. IR spectra revealed the characteristic vibrational and stretching bands due to trigonal and tetrahedral borate network. Slight changes were caused by gamma irradiation in the intensities of the characteristic infrared borate bands and zirconium bands. Irradiated samples developed a noticeable absorption band similar to the F-band familiar in alkali halide crystals which clearly indicated that successive irradiation produced defects in the glass material. Substitution of ZrO2 to the glass matrix suppressed the formation of visible absorption band formed by irradiation whereas no extra peak was observed in the spectral regions. A nonlinear trend was ascribed in the energy band gap values due to the creation of more number of non-bridging oxygen atoms. Emission spectra showed five emission bands corresponding to the zirconium ions which decreased to a very low intensity with a red shift after irradiation. Matching the colour co-ordinates bright blue emission was found for 5 mol% ZrO2 in both irradiated and non irradiated sample.

Determination of the melting temperature of spherical nanoparticles in dilute solution as a function of their radius by exclusively using the small-angle X-ray scattering technique

In this investigation the dependence on radius of the melting temperature of dilute sets of spherical nanocrystals with wide radius distributions was determined by a novel procedure exclusively using the results of small-angle X-ray scattering (SAXS) measurements. This procedure is based on the sensitivity of the SAXS function to small and rather sharp variations in the size and electron density of nanocrystals at their melting temperature. The input for this procedure is a set of experimental SAXS intensity functions at selected q values for varying sample temperatures. In practice, the sample is heated from a minimum temperature, lower than the melting temperature of the smallest nanocrystals, up to a temperature higher than the melting temperature of the largest nanocrystals. The SAXS intensity is recorded in situ at different temperatures during the heating process. This novel procedure was applied to three samples composed of dilute sets of spherical Bi nanocrystals with wide radius distributions embedded in a sodium borate glass. The function relating the melting temperature of Bi nanocrystals with their radius – determined by using the procedure proposed here – agrees very well with the results reported in previous experimental studies using different methods. The results reported here also evidence the predicted size-dependent contraction of Bi nanocrystals induced by the large surface-to-volume ratio of small nanocrystals and an additional size-independent compressive stress caused by the solid glass matrix in which liquid Bi nanodroplets are initially formed. This last effect is a consequence of the increase in the volume of Bi nanoparticles upon crystallization and also of differences in the thermal expansion coefficients of the crystalline phase of Bi and the glass matrix. This additional stress leads to a depression of about 10 K in the melting temperature of the Bi nanocrystals confined in the glass. The procedure described here also allowed the determination of the specific masses and thermal expansion coefficients of Bi nanoparticles in both liquid and crystalline phases.

The role of cadmium oxides in the enhancement of radiation shielding capacities for alkali borate glasses

The radiation shielding capacity of 80B2O3–(20-x) Na2O–x CdO (where x = 0, 2, 4, 6, 8, 10, 12 and 14 mol%) cadmium-doped sodium borate glasses was evaluated. The linear attenuation coefficient (LAC) of the studied glasses was simulated using the Monte Carlo simulation code (MCNP-5) for gamma photons with energy between 0.01 and 15 MeV. Other pivotal gamma ray shielding parameters such as mass attenuation coefficient (MAC), half value layer (HVL), effective atomic number (Zeff), and buildup factors (EBF and EABF) for the selected cadmium-doped sodium borate glasses were examined. The achieved data showed that, BNC 8 glass with CdO contents of 14 mol % possesses the highest LAC and varied between 0.0650 and 83.636 cm-1 and also it has thinner HVL than other BNC glasses and varied between 0.008 and 10.686 cm for gamma ray energy between 0.01 and 15 MeV. Moreover, the removal cross sections of fast neutrons (ΣR) were also calculated theoretically for the selected cadmium-doped sodium borate glasses. The obtained data shows that the insertion of CdO appears to enhance gamma ray and neutron shielding capacity. BNC8 with CdO content (14 mol%) was found to possess the best shielding parameters among the studied cadmium-doped sodium borate glasses.

Understanding the role of post-indentation recovery on the hardness of glasses: Case of silica, borate, and borosilicate glasses

Hardness is an important property of glasses, which depends strongly on the method of measurement. Herein, we estimate the hardness of three oxide glasses, namely, pure silica (0B), borosilicate (37B), and sodium borate (75B) glass samples at micro and nanoscale. We observe that annealing of these glass samples, after polishing, has little effect on their hardness and modulus. Interestingly, we observe that the nanoindentation is unable to capture the full extent of elastic recovery, thereby underestimating the hardness of these glasses. We show that the post-indentation elastic recovery is highly dependent on the chemical composition of glass. Combining nanoindentation and atomic force microscopy (AFM) imaging, we accurately capture the complete elastic recovery of glass samples, thereby calculating the true hardness values from indentation depth profiles. Overall, we show that post-indentation elastic recovery plays a crucial role in determining the hardness of glasses.

Wear Resistance of Niobium Carbide Layers Produced on Gray Cast Iron by Thermoreactive Treatments

Gray cast iron is commonly used due to its high damping capacity, machinability and low cost, due to the presence of free graphite and the high fluidity of the molten metal which facilitates the casting of complex parts with thin walls. Suitable coatings can increase gray cast iron wear resistance and expand its usage range. The high hardness of niobium carbide indicates that it may be a good candidate for this purpose. In this work, samples of gray cast iron with composition 3.47% C-2.39% Si-0.55% Mn-0.15% Ni-0.65% Cu-balance Fe were subjected to two thermoreactive niobizing treatments. The first process (a pack treatment) utilized a powder mixture composed of iron niobium, NH4Cl, Al2O3 at 900 °C during 2 h. The second treatment, a thermoreactive deposition process (TRD), utilized a liquid molten bath of sodium borate and iron niobium performed at 900 °C for 2 h. X-ray diffraction (XRD), Vickers hardness, micro-adhesive (fixed-ball) and micro-abrasive (free-ball) wear tests were used to characterize the treated samples. Hardness layers of 2000 HV, typical for niobium carbides, were obtained. Wear tests demonstrated a substantial increase (2 to 12 times higher than that the substrate) in wear resistance obtained with niobizing treatments.

Predicting Ionic Diffusion in Glass from Its Relaxation Behavior.

In low-viscosity liquids, diffusion is inversely related to viscosity via the Stokes-Einstein relation. However, the Stokes-Einstein relation breaks down near the glass transition as the supercooled liquid transitions into the non-ergodic glassy state. The nonequilibrium viscosity of glass is governed by the liquid-state viscous properties, namely, the glass transition temperature and the fragility. Here, a model is derived to predict the ionic diffusivity of a glass from its nonequilibrium viscosity, accounting for the compositional dependence of the glass. The free energy activation barrier for diffusion is related to the activation enthalpy for viscous flow using the Mauro-Allan-Potuzak model of nonequilibrium viscosity [Mauro, J. C.; Allan, D. C.; Potuzak, M. Nonequilibrium Viscosity of Glass. Phys. Rev. B 2009, 80, 094204]. These insights allow for accurate prediction of activation barriers for diffusion of alkali ions. The model is supported by experimental results and nudged-elastic band calculations applied to sodium silicate and borate glasses.

Effects of Retarding Admixture, Superplasticizer and Supplementary Cementitious Material on the Rheology and Mechanical Properties of High Strength Calcium Sulfoaluminate Cement Paste

In this paper, the effects of retarding admixture, polycarboxylate (PCE) superplasticizer and supplementary cementitious material (SCM) on the rheology of high strength calcium sulfoaluminate (CSA) cement paste are investigated. At the water to binder ratio of 0.3, one PCE, two retarding admixtures, and three SCMs were used in the test. The test results show that much more PCE is needed for paste with citric acid than that with sodium borate to achieve a similar initial flowability. The reference paste and pastes mixed with sodium borate or fly ash exhibit shear thickening; pastes mixed with citric acid or silica fume exhibit shear thinning. The addition of citric acid increases the maximum shear stress of pastes, while the maximum shear stress can be significantly reduced by silica fume. Both the retarding admixtures and SCMs will strongly reduce the early-age compressive strength of the cement paste. At 28 days of age, CSA cement paste incorporating retarding admixtures has comparable strength to the reference paste. Silica fume has less negative effect on the compressive strength of the CSA cement paste due to the significant filling effect.

Precise and rapid isotopic analysis of lithium in refractory materials using NaLiBO2+ by thermal ionization mass spectrometry (TIMS)

6Li/7Li isotopic ratio was determined in lithium based compounds and refractory materials by TIMS using a novel approach. The method involved fusion of the samples such as Lithium Aluminate (LiAlO2), Lithium Titanate (Li2TiO3), Lithium Carbonate etc, with Sodium Borate flux directly on the loading filament to produce NaLiBO2+ ions at m/z 71,72 and 73 and Na2BO2+ at m/z 88 and 89. 6Li/7Li was determined by monitoring NaLiBO2+ ions at m/z 71, 72 and 73. Contributions from isotopes of boron to the ion intensity at m/z 71–73, were accounted by sequentially monitoring Na2BO2+, at m/z 88 and 89 during same analysis. L-SVEC Li2CO3was used for the initial investigations to identify the optimum composition of the analyte, sodium borate mixture required for obtaining precise 6Li/7Li ratio and the possible ion formation mechanism. Fusion of the lithium compounds with boron rich sodium borates having compositions such as Na2O·5B2O3 and Na2O·10B2O3 resulted in strong and stable molecular ion intensities for both NaLiBO2+ and Na2BO2+. Average 6Li/7Li isotopic ratio obtained for L-SVEC lithium from ten measurement using this technique was 0.08277 ± 0.00006 (S.D). Refractory compounds Li2TiO3 and LiAlO2 and lithium salts such as Li2CO3 (lithium source for the refractory compounds) and Li2B10O16 were analysed for 6Li/7Li isotopic ratio with precision of better than 0.07% (% R.S.D). Agreement between the 6Li/7Li isotopic ratio of the refractory compound and the starting material signified that there is no matrix induced mass bias. This technique not only resulted precise values for 6Li/7Li isotopic ratio but has also simplified the procedure for isotopic analysis of Li in refractory materials by circumventing the dissolution and purification step that would have been otherwise required for established mass spectrometric methods.

Role of constituents for the chirality isolation of single-walled carbon nanotubes by the reversible phase transition of a thermoresponsive polymer.

The simple sorting procedure and continuous use of poly(N-isopropylacrylamide) (PNIPAM), a well-known thermoresponsive polymer, have a high potential for the mass production of single-walled carbon nanotubes (SWCNTs) with a specific electronic structure. However, knowledge of efficient single-chirality sorting methods with mixed surfactant systems is not applicable. In this work, we explored experimental conditions by controlling the interaction among PNIPAM, sodium cholate (SC) and SWCNTs. An optimization of the PNIPAM and SC concentrations as well as the addition of sodium borate achieved the selective release of (6,4) nanotubes into the liquid phase after the PNIPAM phase transition. The sorting mechanism with PNIPAM was explained by the difference in the micelle configuration on the SWCNTs and the hydrophobic collapse of PNIPAM in the presence of a sodium salt. The one-step sorting procedure for obtaining SWCNTs with a single chirality via PNIPAM will help promote their widespread application.

Formation of samarium(II) in synthetic sborgite prepared in air at low temperature

A mixture of boric acid combined with trivalent samarium doped sodium borate was fired in air at 450 °C. The addition of water to the hot residue resulted in the generation of a product in which the incorporated samarium has been reduced from the trivalent form to the divalent state as identified by emission spectroscopy. This product has been identified as a synthetic form of the mineral sborgite. The divalent samarium emission appears to result from the samarium ion occupying a boron site in the material.

Oxidative and Frictional Behavior of a Binary Sodium Borate–Silicate Composite in High-Temperature Lubricant Applications

Alkaline borate–silicate composites provide desirable protection for the machinery moving contacts in high-temperature coating and lubricant applications, but their behavior depends closely on the ...

Mechanisms of Pressure-Induced Structural Transformation in Confined Sodium Borate Glasses.

In this paper, density functional theory simulations were conducted to investigate the structural adaptation of sodium borates xNa2O·(100-x)B2O3 (x = 25, 33, 50, and 60 mol %) during the compression/decompression between 0 and 10 GPa. The sodium borates are confined between two Fe2O3 substrates and undergo the compression by reducing the gap between the two surfaces. The results reveal the borate response to the load through a two-stage transformation: rearrangement at low pressure and polymerization at high pressure. The pressure required to initiate the polymerization depends directly on the portion of fourfold-coordinated ([4]B) boron in the sodium borates. We found that the polymerization occurs through three different mechanisms to form BO4 tetrahedra with surface oxygen and nonbridging and bridging oxygen. The electronic structure was analyzed to understand the nature of these mechanisms. The conversions from BO3 to BO4 are mostly irreversible as a large number of newly formed BO4 remain unchanged under the decompression. In addition, the formation of a sodium-rich layer can be observed when the systems were compressed to high pressure. Our simulation provides insight into sodium borate glass responses to extreme condition and the underlying electronic mechanisms that can account for these behaviors.

Effect of Sodium Borate on the Preparation of TiN from Titanomagnetite Concentrates by Carbothermic Reduction–Magnetic Separation and Acid Leaching Process

Carbothermic reduction–magnetic separation and acid leaching processes were used to produce TiN and direct reduced iron (DRI) from titanomagnetite concentrates. The effects of sodium borate on the reduction behavior of TMCs, the magnetic separation of the reduced products, and the purification of the impure TiN by acid leaching were investigated. Results of x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis showed that magnesium aluminate spinel (MgAl2O4) was generated in the reduced products, which could hinder the purification of the TiN. Adding sodium borate not only inhibited the formation of MgAl2O4, but also promoted the formation of TiN by decreasing the roasting temperature and time. Adding sodium borate slightly affected the separation of metallic Fe and TiN. By adding 16% sodium borate, a DRI with 94.3% Fe, 0.6% Ti, and 0.1% V was obtained by magnetic separation. After HCl + HF leaching, the TiN product containing 74.1% Ti and 2.8% V was obtained with the Ti recovery of 94.6% and V recovery of 58.3%.

Micellar Electrokinetic Chromatography Method Development for Sensitive Monitoring of Rotenone in Lake Waters

Rotenone, a naturally occurring isoflavone compound, is applied to water as a piscicide to manage undesired fish populations in lakes, ponds, rivers and in aquaculture. A rapid and sensitive method based on solid-phase extraction (SPE) combined with large-volume sample stacking with polarity switching (LVSS) and micellar electrokinetic chromatography (MEKC) has been developed for the identification and quantification of rotenone in lake water. Several experimental parameters for MEKC, LVSS and SPE were investigated to achieve the optimum conditions necessary for the analysis. The optimized conditions which included a background electrolyte containing 20 mM sodium borate and 25 mM sodium dodecyl sulfate (SDS) at pH 10 were used to successfully detect rotenone within 17 min. Using a combined SPE and LVSS approach, the rotenone signal was enhanced by 1000-fold compared with a normal capillary electrophoresis analysis, and limits of detection and quantification obtained were 3 and 10 μg L−1, respectively. The calibration curve was linear for rotenone concentration over the range of 10–100 μg L−1 and the method was highly reproducible with the relative standard deviation of the peak areas and migration times for method intra-day repeatability (n = 6) found to be 5.4% and 0.6%, respectively. Quantitative recoveries ranging from 85 to 88% were obtained in the lake water matrices. The potential of the proposed method to be used for quantitative determination of rotenone at trace level concentrations in water samples was demonstrated by analyzing lake water samples including surface (1 m) and bottom (13 m), which makes it a suitable practical method for analyzing rotenone residues in water.

Simultaneous upgrading of biomass-derived sugars to HMF/furfural via enzymatically isomerized ketose intermediates

BackgroundRecently, exploring fermentative or chemical pathways that convert biomass-derived sugars to fuels/chemicals has attracted a lot of interest from many researchers. We are investigating a hydrocarbon pathway from mixed sugars via 5-hydroxymethyl furfural (HMF) and furfural intermediates. To achieve this goal, we must first convert glucose and xylose to HMF and furfural in favorable yields. Current processes to produce HMF/furfural generally involve the use of acid catalysts in biphasic systems or solvents such as ionic liquids. However, the yield from transforming glucose to HMF is lower than the yield of furfural from xylose.ResultsIn this study, we present an efficient chemical pathway simultaneously transforming glucose and xylose to HMF and furfural via ketose intermediates, i.e., fructose and xylulose, which were generated from glucose and xylose via enzymatic isomerization. In the enzymatic isomerization, by adding sodium borate to complex with the ketoses, xylose conversion reached equilibrium after 2 h with a conversion of 91% and glucose conversion reached 84% after 4 h. By enzymatically isomerizing the aldoses to ketoses, the following dehydration reactions to HMF and furfural could be performed at low process temperatures (i.e., 110–120 °C) minimizing the side reactions of the sugars and limiting the degradation of furfurals to humins and carboxylic acids. At 120 °C, pH 0.5, and 15 min reaction time, mixed ketose sugars were converted to HMF and furfural in yields of 77% and 96%, respectively (based on starting aldose concentrations).ConclusionTaken together, our results demonstrate that this combined biological and chemical process could be an effective pathway to simultaneously convert biomass-derived glucose and xylose to HMF and furfural, for use as intermediates in the production of hydrocarbons.

Influence of cobalt ions on the structure, phonon emission, phonon absorption and ligand field of some sodium borate glasses

To study some effects of cobalt cations on some properties of a glass system, new glass formulation [75% B2O3 – 5% Al2O3 – (20–x) %Na2O – (x) % CoCl2], where x = 0, 1, 2, 3 and 4 mol% was obtained via melt quenching method. X-ray diffraction (XRD) results emphasize the amorphous nature. The glasses' internal structure was examined via Fourier transform infrared (FTIR). The dependence of density (⍴), boron to boron separation (dB-B), molar volume (Vm), optical absorbance (A), Urbach energy (EU) and band gap (Eg) on Co2+ cations content was scrutinized. The trend of density (⍴), molar volume (Vm), optical absorbance (A), and Urbach energy (EU) shows an increasing behavior, while band gap (Eg) exhibits a decrement behavior with CuCl2 content. The optical absorption coefficient was employed to calculate Eg using the phonon emission and absorption. The crystal field (10Dq), Racah parameters (B and C) and the nephelauxetic ratio will be obtained from optical absorption spectra. According to the obtained results, the sample that contains 4% mol. of CoCl2 has the highest density, molar volume and the least band gap.

Ab initio study on physical and chemical interactions at borates and iron oxide interface at high temperature

Ab initio molecular dynamics (AIMD) simulations were carried out to study the interactions of sodium tetraborate (Na2B4O7) and boron oxide (B2O3) on an iron oxide surface Fe2O3(0 0 0 1) at 1073 K. The results demonstrate that high temperature transforms Na2B4O7 structure by activating sodium mobility and decomposing BO4 complexes into BO3 and non-bridging oxygen. These products engage in chemical reactions with the Fe2O3 surface by forming O–Na ionic and Fe–O–B covalent bonds, which make Na2B4O7 adhere extremely well on the surface. Density profile and charge analysis show that sodium cations play a critical role at the interface by forming O–Na–O stacking and acting as a bridge to connect the negatively charged areas of the O-rich surface and the oxygen of the borate. On the contrary, the molten B2O3 remains intact with no chemical reactions which accounts for its poor adhesion on the Fe2O3 surface. Furthermore, the Blue Moon method was applied to predict bond dissociation and charge analysis was used to rationalize the differences in binding mechanisms at the lubricant-steel interfaces. The above simulations provide a theoretical interpretation for the lubricity of sodium borate and boron oxide at elevated temperature.

Dynamic Color-Switching of Plasmonic Nanoparticle Films.

The fast and reversible switching of plasmonic color holds great promise for many applications, while its realization has been mainly limited to solution phases, achieving solid-state plasmonic color-switching has remained a significant challenge owing to the lack of strategies in dynamically controlling the nanoparticle separation and their plasmonic coupling. Herein, we report a novel strategy to fabricate plasmonic color-switchable silver nanoparticle (AgNP) films. Using poly(acrylic acid) (PAA) as the capping ligand and sodium borate as the salt, the borate hydrolyzes rapidly in response to moisture and produces OH- ions, which subsequently deprotonate the PAA on AgNPs, change the surface charge, and enable reversible tuning of the plasmonic coupling among adjacent AgNPs to exhibit plasmonic color-switching. Such plasmonic films can be printed as high-resolution invisible patterns, which can be readily revealed with high contrast by exposure to trace amounts of water vapor.

Dynamic Color‐Switching of Plasmonic Nanoparticle Films

AbstractThe fast and reversible switching of plasmonic color holds great promise for many applications, while its realization has been mainly limited to solution phases, achieving solid‐state plasmonic color‐switching has remained a significant challenge owing to the lack of strategies in dynamically controlling the nanoparticle separation and their plasmonic coupling. Herein, we report a novel strategy to fabricate plasmonic color‐switchable silver nanoparticle (AgNP) films. Using poly(acrylic acid) (PAA) as the capping ligand and sodium borate as the salt, the borate hydrolyzes rapidly in response to moisture and produces OH− ions, which subsequently deprotonate the PAA on AgNPs, change the surface charge, and enable reversible tuning of the plasmonic coupling among adjacent AgNPs to exhibit plasmonic color‐switching. Such plasmonic films can be printed as high‐resolution invisible patterns, which can be readily revealed with high contrast by exposure to trace amounts of water vapor.