Molar Ratio Of Citric Acid Research Articles

Synthesis and Properties of a Red Na5Zn2Gd1−x(MoO4)6: xEu3+ Phosphor

Novel Eu3+-doped Na5Zn2Gd(MoO4)6 triple molybdate phosphors were fabricated by the sol-gel method. The structure, morphology, and luminescent properties have been characterized by X-ray diffraction (XRD), thermogravimetric differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), FTIR spectroscopy, and luminescence spectroscopy. The results indicated that the synthesized Na5Zn2Gd1−x(MoO4)6: xEu3+ phosphor consisted of a pure phase with monoclinic structure. Under excitation at 465 nm, the Na5Zn2Gd1−x(MoO4)6: xEu3+ phosphor exhibits an intensive red emission band around 610 nm corresponding to the transition of 5D0→7F2 which is much higher than that 5D0→7F1 at 594 nm, which was appropriate for a blue LED. According to the influence of the synthesis conditions, the phosphors showed the highest emission intensity when the doping concentration of Eu3+ was 25 mol.% and the molar ratio of citric acid to metal ions was 2:1. Na5Zn2Gd0.75(MoO4)6: 0.25 Eu3+ with the color coordinates (x = 0.658, y = 0.341) is a more stable red phosphor for blue-based white LEDs than the commercial Y2O2S: Eu3+ red phosphor (0.48, 0.50) due to its being closer to the NTSC standard values (0.670, 0.330).

Solid-State Fluorescent Carbon Dots with Hydrophobic Modification Induced Red Emission for White Light-Emitting Diodes.

Herein, we developed red solid-state fluorescent carbon dots (SSF-CDs) through a one-step solvothermal method, utilizing acetone as the carbonization solvent. Optical and structural characterization revealed that the sp2 domains in the core of the R-CDs were consistently interrupted and that the oxygen-containing groups on the surface were replaced by alkyl groups. This substitution mitigates excessive π-π interactions, thereby preventing quenching of fluorescence in the solid state. Adjusting the molar ratio of citric acid (CA) and urea yielded solid fluorescent carbon dots (CDs) with panchromatic luminescence, indicating enhanced π-π interactions and more pronounced red shifts in the emission peaks. Furthermore, we found that this strategy is applicable to other carbon sources, including phenylenediamine, salicylic acid, and lignin. This research presents an innovative strategy for the fabrication of solid-state luminescent CDs.

Synthesis and Characterization of LaMnO3 Prepared by Hydrothermal Synthesis Method

Abstract LaMnO3 powders were prepared by hydrothermal synthesis method by varying citric acid to metal ions. The ratio of citric acid to metal ions is one of the parameters that have an affect on purity of LaMnO3 prepared by hydrothermal method. It is necessary to control the parameter to obtain the good quality of the final product of LaMnO3. LaMnO3 with variation molar ratio of citric acid to metal ion (CA/M) of 0, 1 and 4 were prepared. To determine the morphology, crystall structure, and phase composition, the powders were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) techniques. The obtained results revealed that the morphology of sample CA/M = 0 has rod-like shape, CA/M = 1 was in the formed of irregular fine particles that stuck together and formed agglomerates, while the spherical morphology with various diameters were formed in the sample CA/M = 4. The XRD analysis demonstrated that sample CA/M = 1 had a single phase while in sample CA/M = 0 and CA/M = 4 others phase were detected such as La (OH)3 and La2O3. There was a change in crystall structure of the LaMnO3 phase in each sample due to the presence of citric acid. The peaks position in sample CA/M = 0, 1, dan 4 exhibit orthorhombic, rhombohendral and cubic structure with space group of Pnma, R -3c and Pm-3m respectively.

Synthesis of BaAl2Ge2O8 by the Pechini method, using graphene oxide as stabilizing agent

In this study, BaAl2Ge2O8 (BAG) synthesis was performed using the Pechini method for the first time. Graphene oxide (GO), used as a precursor agent to obtain the pure phase of BAG, was incorporated to the precursor powders before heath treatment at 1300 °C. The pure BAG phase was obtained with a cation:citric acid molar ratio of 8:1, a pH = 8, and a mass concentration of GO from 0.5 wt%. The incorporation of 2 wt% of GO promoted the formation of irregular-shaped BAG flakes with a size smaller than 3 µm. The pure BAG phase exhibited a band gap of 5.12 eV.

Modulating surface functional groups in carbon dots for enhanced inhibition of β‐amyloid aggregation

AbstractGaining a profound understanding of carbon dots (CDs) structure and their potential to inhibit β‐amyloid (Aβ) aggregation holds significant importance in the quest for Alzheimer's disease (AD) prevention and treatment. Herein, CDs with varying structures were synthesized by adjusting the molar ratio of citric acid (CA) and ethylenediamine (EDA). Transmission electron microscopy (TEM) was used to characterize their size and morphology. Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS) were applied to study their structure. Optical properties were analyzed through Ultraviolet (UV) spectroscopy absorption and fluorescence spectroscopy. The inhibitory effect of CDs on Aβ1–42 aggregation was explored using circular dichroism and atomic force microscopy (AFM). The results highlighted the substantial influence of the CA to EDA molar ratio on the surface structure of CDs, subsequently impacting their optical properties and efficacy in inhibiting Aβ1–42 aggregation. With increasing EDA content, CDs exhibited a rise in the number of amino functional groups while experiencing a reduction in carboxyl groups. CDs possessing more amino functional groups effectively induced alterations in the initial conformation of Aβ1–42, leading to a significant inhibition of Aβ1–42 aggregation.

Magnesium Hydrogen-generating Materials and a Hydrogen Generation Setup

The reaction of composites consisting of MgH2 and a graphene-like or nickel–graphene material with water or citric acid solutions of various concentrations was studied. The composites were prepared by mechanochemical treatment in a hydrogen atmosphere. The reaction of an aqueous citric acid solution with the composites is fast: 98% hydrogen yield is reached at the MgH2 : citric acid molar ratio of 1 : 1. A setup for preparing compressed hydrogen from the composites was developed. It can be used in autonomous mobile installations for hydrogen generation under high pressure, followed by filling balloons.

Red-Emissive Center Formation within Carbon Dots Based on Citric Acid and Formamide.

The formation of red-emissive optical centers in carbon dots based on citric acid and formamide was investigated by varying the synthesis parameters with focus on finding optimal─necessary and sufficient─amount of precursors to decrease byproduct amount and to increase the chemical yield of red-emissive carbon dots. The emission is observed at 640 nm excited at 590 nm and quantum yield reaches up 19%. A high chemical yield of carbon dots of 26% was achieved at an optimal molar ratio of citric acid to formamide of 1:4.

Performance of Cu/ZnO/Al2O3 Catalysts Prepared by Sol–Gel Methods on Methanol Steam Reforming

Cu/ZnO/Al2O3 catalysts were prepared for online methanol steam reforming (MSR) using a conventional sol–gel method in this study. The optimal preparation conditions, including the calcination temperature, Cu loading, molar ratio of citric acid to metal ions (CA/M), and pH, were investigated. CZA50 exhibited the highest MSR activity among all catalysts. It was prepared at a calcination temperature of 350 °C; Cu, Zn, and Al molar fractions of 50%, 30%, and 20%; CA/M of 1.5; and without adjusting pH. Furthermore, a modified sol–gel method was proposed to enhance the mechanical strength of Cu/ZnO/Al2O3 catalysts by using γ-Al2O3 powders as catalyst precursors instead of aluminum nitrates. In this modified method, part of Cu2+ and Zn2+ ions were impregnated firstly on γ-Al2O3 powders, and then the remaining metal ions formed sol–gel with citric acid. MCZA-0.25 catalysts prepared by this modified method showed superior catalytic activity at an Al/(Cu+Zn) ratio of 0.25. The methanol conversion rates of CZA50, MCZA-025, and CZA-Commercial were 82.9%, 79.4%, and 74.7% at the temperature of 200 °C and methanol liquid phase space velocity (LHSV) of 1.0/h, respectively. The average crushing strength of CZA50, MCZA-0.25, and CZA-Commercial were measured as 28 N/cm, 37 N/cm, and 32 N/cm, respectively.

Role of WSOCs and pH on Ammonium Nitrate Aerosol Efflorescence: Insights into Secondary Aerosol Formation.

Efflorescence of ammonium nitrate (AN) aerosols significantly impacts atmospheric secondary aerosol formation, climate, and human health. We investigated the effect of representative water-soluble organic compounds (WSOCs) (sucralose (SUC), glycerol (GLY), and citric acid (CA) on AN:WSOC aerosol efflorescence using vacuum Fourier transform infrared spectroscopy. Combining efflorescence relative humidity (ERH) measurements, heterogeneous nucleation rates, and model predictions, we found that aerosol viscosity, correlating with molecular diffusion, effectively predicted ERH variations among the AN:WSOC aerosols. WSOCs with higher viscosity (SUC and CA) hindered efflorescence, while GLY with a lower viscosity showed a minor effect. At a low AN:CA molar ratio (10:1), CA promoted ERH, likely due to CA crystallization. Increasing the droplet pH inhibited AN:CA aerosol efflorescence. In contrast, for AN:SUC and AN:GLY aerosols, efflorescence is pH-insensitive. With the addition of trivial sulfate, AN:SUC droplets exhibited two-stage efflorescence, coinciding with ammonium sulfate and AN efflorescence. Given the atmospheric abundance, the morphology, phase, and mixing state of nitrate aerosols are significant for atmospheric chemistry and physics. Our results suggest that AN:WSOCs aerosols can exist in the amorphous phase in the atmosphere, with efflorescence behavior depending on the aerosol composition, viscosity, pH, and the cation and anion interactions in a complex manner.

Acid catalyzed microwave-assisted production of full-color light emissive carbon quantum dots for CCT-tunable WLEDs

Many studies have examined the use of multicolor light emissive carbon quantum dots (CQDs) in toxic metal-free optoelectronic devices, but it is still limited to obtain desirable optical properties. Here, we present a straightforward synthetic route for producing multicolor light emissive nitrogen-doped carbon quantum dots (NCQDs) using a microwave-assisted process, thus yielding individual color emissions of NCQDs in a batch. The emissive colors from NCQDs can be controlled by adjusting the molar ratios of citric acid and urea from 1 to 6 for blue and green-light emission, respectively. When o-phenylenediamine (oPDA) was chosen as a precursor, the resulting NCQDs can emit yellow light, while the red light emissive NCQDs can be obtained in the presence of a diluted HCl as a catalyst for accelerating and extending sp2-carbon bonding. The doped nitrogen in NCQDs was found to be formed as a graphitic nitrogen in the core, leading to red-shifted photoluminescent emissions from 450 nm to 620 nm. To fabricate white-light emitting diodes (WLEDs), the mixing ratios of NCQDs with different light emissions in polydimethylsiloxane (PDMS) were varied to control the correlated color temperature (CCT) from 3386 K to 7151 K and CIE coordinates of (0.30, 0.32), (0.32, 0.36), and (0.40, 0.37).

The effect of the citric acid to metal nitrates molar ratio on the structural and magnetic properties of strontium hexaferrite nanoparticles synthesized by the sol-gel combustion method

Strontium hexaferrite is a hard ferrite with the chemical formula of SrFe12O19 and has a magnetoplumbite structure. Due to high anisotropy, high saturation magnetization, chemical stability, high corrosion resistance, and appropriate Curie temperature, it has been widely used as a permanent magnetic material. A novel sol-gel combustion process was used to synthesize ultrafine particles of strontium hexaferrite. The weight ratio of citric acid to the total weight of strontium and iron salts nitrate (CA/MN) is among the parameters affecting the purity of SrFe12O19 nanoparticles produced by the sol-gel method, which can improve the purity of the final product by controlling this parameter. M-type SrFe12O19 nanostructures with different citric acid to metal nitrates molar ratios (0.5, 1, 2, and 4) were prepared. The results showed that nitrate-citrate gels exhibit self-ignition behavior after combustion in the air at room temperature. The samples were then characterized by XRD, TGA/DTA, FTIR, FE-SEM, VSM. The results showed that the crystallite size of strontium hexaferrite is significantly affected by the molar ratio of citric acid to metal nitrates. As the molar ratio of citric acid to metal nitrates increases, the size of nanostructures decreases. By increasing the molar ratio of citric acid from 0.5 to 1, the saturation magnetization and magnetic remanence magnetization increase, but the coercive field decreases.

Thermoplastic starch/polyvinyl alcohol blends modification by citric acid–glycerol polyesters

Thermoplastic starch/polyvinyl alcohol (TPS/PVA) films have limitations for being used in long–term applications due to starch retrogradation. This leads to plasticizer migration, especially when low molecular weight plasticizers such as glycerol, are used. In this work, we employed mixtures of oligomers based on glycerol citrates with higher molecular weight than glycerol as plasticizers for potato–based TPS/PVA blends obtained by melt–mixing. This constitutes an alternative to reduce plasticizer migration while keeping high swelling degree, and to provide high mechanical performance. The novelty lies in the usage of these oligomers by melt-mixing technique, aspect not deeply explored previously and that represents the first step towards industrial scalability. Prior to the blending process, oligomers mixtures were prepared with different molar ratios of citric acid (0–40 mol%) and added them. This minimizes the undesirable hydrolysis effect of free carboxylic groups on starch chains. The results demonstrated that the migration of plasticizers in TPS/PVA blends decreased by up to 70 % when the citric acid content increased. This reduction was attributed to the higher molecular weight (the majority in the range 764–2060 Da) and the 3D structure of the oligomers compared to using raw glycerol. Furthermore, the films exhibited a 150 % increase in Young's modulus and tensile strength without a reduction in elongation at break, while maintaining a high gel content, due to a moderate crosslinking.

Extraction and separation of vanadium (IV) by EHEHPA with citric acid complexing iron (III) from sulfate leaching solution

The recovery of vanadium from sulfate leaching solutions is crucial for resource sustainability and environmental protection. However, the leaching solution contains impurities such as Fe (III), which have a significant impact on the separation and enrichment of V because a) the separation of Fe (III) and V (IV) through solvent extraction is problematic, and b) in the presence of oxygen from the air, it is challenging to fully reduce Fe (III) to Fe (II). Citric acid was used as a complexing agent in the aqueous phase to complex the Fe (III), and the effect of V (IV) extraction using 2-Ethylhexylphosphoric acid mono-2-ethylhexyl ester (EHEHPA) after Fe (III) complexation was investigated. To determine the complexation dose necessary for complete Fe (III) complexation, the numbers of ligands in the citric acid and Fe (III) complex were estimated, and the complexation mechanism of citric acid with Fe (III) was further clarified using UV–vis and FT-IR. According to the experimental findings, citric acid exhibits better complexing action than other complexing agents. Citric acid may complex > 96 % of Fe (III) in the liquid phase when the molar ratio of citric acid to Fe (III) is 1.5. When the pH of the solution was 1.2 and the molar ratio of citric acid to Fe (III) was 2, the extraction rates of V (IV) and Fe (III) obtained through EHEHPA were > 80 % and < 1 %, respectively. Additionally, the maximum separation factor βV/Fe was 430, which helped achieve the complete removal of Fe (III).

Effect of Ethylene Glycol: Citric Acid Molar Ratio and pH on the Morphology, Vibrational, Optical and Electronic Properties of TiO2 and CuO Powders Synthesized by Pechini Method.

High-purity TiO2 and CuO powders were synthesized by the Pechini method, an inexpensive and easy-to-implement procedure to synthetize metal oxides. The variables of synthesis were the ethylene glycol:citric acid molar ratio and the pH. High reproducibility of the anatase and tenorite phase was obtained for all synthesis routes. The degree of purity of the powders was confirmed by XRD, FTIR, UV-Vis absorption and XPS spectra. SEM and TEM images revealed the powders are composed of micrometer grains that can have a spherical shape (only in the TiO2) or formed by a non-compacted nanocrystalline conglomerate. FTIR spectra only displayed vibrational modes associating TiO2 and CuO with nanoparticle behavior. UV-Vis absorption spectra revealed the values of maximum absorbance percentage of both systems are reached in the ultraviolet region, with percentages above 83% throughout the entire visible light spectrum for the CuO system, a relevant result for solar cell applications. Finally, XPS experiments allow the observation of the valence bands and the calculation of the energy bands of all oxides.

Thermosetting environment‐friendly polyamide adhesives prepared with citric acid and hexanediamine

AbstractThermosetting polyamide resins prepared by reacting citric acid with hexanediamine (CH) were synthesized and used for plywood bonding in this work, and the effects of reaction time, molar ratio of citric acid, and hexanediamine on the bonding performance have been studied. Fourier transform‐infrared (FT‐IR) and liquid chromatography‐mass spectrometry (LC–MS) were used to determine the structures of the resins. Differential scanning calorimeter (DSC), dynamic mechanical properties (DMA), and thermogravimetric analysis (TG) were used to analyze its thermal properties. The results show that amide bonds can be formed by the reaction of carboxyl and amino groups, which acted as reaction raw materials that can undergo further polycondensation to render possible the formation of a cured cross‐linked network, thus to ensure the bonding performance of the adhesives. Meanwhile, CH adhesives presented excellent bonding strength and water resistance above the standard requirements (≥0.7 MPa). In particular, the plywood prepared by CH resin with molar ratio of citric acid to hexanediamine of 1:1.5 and reaction time of 3 h exhibited the best performance, the dry shear strength being as high as 1.96 MPa, 24 h cold water soaking strength of 0.87 MPa, and 3 h hot water (63°C) soaking wet strength attaining 1.24 MPa.

Composition and concentration-dependent photoluminescence of nitrogen-doped carbon dots

Photoluminescent carbon dots have received significant research interest in recent years owing to their extraordinary optical properties, biocompatibility, and versatile functionalities. Nitrogen-doping is a widely used strategy for enhancing the photo-electronic functionalities of carbon dots. However, there is a lack of systematic study on the composition and concentration-dependency emission behaviour of N-doped carbon dots in the literature. In this study, multicolour carbon dots (CDs) having different degree of nitrogen doping were synthesized by varying the molar ratio of citric acid to urea in the precursor via hydrothermal treatment. The effects of nitrogen doping on chemical, optical, and electronic properties of CDs were characterized using various techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR); fluorescence and absorption spectroscopy; fluorescence lifetime and Hall effect measurements. Three main emissive centres were recognized in concentration-dependent fluorescence study of N-CDs which can be ascribed to molecular type of fluorescence, core emission, and mid-gap nitrogen states on the edge/surface of CDs. A plausible mechanism in relation to the obtained results is proposed. This work provides insights on the opto-electro-tunability of CDs via N-doping.

Novel strategy for enhanced visible light-responsive photoactivity of ZnFe2O4 with a single-mode microwave combustion process: Primary parameters

To date, the inferior physicochemical properties of nanomaterials synthesized with a household microwave (MW) oven have been attributed to a large extent to the non-uniform electromagnetic field. Herein, we developed a single-mode MW combustion process (MCP) considering criteria of green chemistry and further annealled the amorphous ZnFe2O4-based sol–gel precursors. The preferred single-mode MCP-based parameters mainly include 7 g : 2 g of the mass ratio (w/w) of SiC : sol–gel precursors, 1 : 1.5 of initial molar ratio of citric acid : metal ions (CA : M), 300 ℃ ∼ 600 ℃ range of the calcination temperature, N2 atmosphere of 3 L/min as well as the washing pretreatment of precursors. Moreover, based on Mössbauer spectroscopy, we infer that the reduction of structural ferric ions into ferrous ions in the lattice resulted in excellent magnetic separation of multiphase heterojunctions ZnO@ZnFe2O4 during a single-mode MCP. Furthermore, the ζ potentials of ZnO@ZnFe2O4 and ZnFe2O4 indicate that cationic dyes could be spontaneously adsorbed onto the negatively charged surface of ZnO@ZnFe2O4. Thus, the visible-light-driven catalytic mechanism of ZnO@ZnFe2O4 was also proposed. Additionally, the aforementioned single-mode MCP strategy could also endow P25-based TiO2 with excellent visible light-responsive photo-activities for effective degradation of estradiol. To our best knowledge, this is the first report associated with a novel single-mode MCP method to endow ZnO@ZnFe2O4 or P25-based TiO2 with an enhanced visible light-responsive (λ ≥ 420 nm) photoactivity.

Green citric acid in the sorption process of rare earth elements

In this study the effects of citric acid (CA) as a biodegradable complexing agent in the sorption process of La(III), Nd(III) and Ho(III) ions (single component systems) on various types of ion exchangers (chelating ion exchangers, cation exchanger, strongly and weakly basic polystyrene and polyacrylate anion exchangers) were investigated. The effects of pH, Ln(III):CA molar ratio, phase contact time and initial concentrations as well as temperature on the adsorption capacity were analysed. The optimal process conditions were also determined which varied depending on the ion exchanger and the metal ion. The process was fast in all systems (up to 60 min). The sorption data was analysed using the pseudo-first order (PFO), pseudo-second order (PSO), intraparticle diffusion (IPD), Boyd and Dumwald–Wagner (DW) kinetic models as well as the Langmuir, Freundlich, and Temkin isotherm models. Among the studied adsorbents, the highest adsorption capacity was obtained for the Purolite S957 chelating ion exchanger which was 162.04 mg/g for the La(III) complexes, 142.65 mg/g for the Nd(III) complexes and 180.26 mg/g for the Ho(III) complexes. Reusability of ion exchangers in the desorption studies was also evaluated as a sustainable approach. Moreover, dynamic experiments were performed using the columns set. The Thomas, Adams–Bohart, Yoon–Nelson and Wolborska models were applied to the experimental data to predict the dynamic behaviour of fixed bed columns. The physicochemical properties of adsorbents were characterized by scanning electron microscopy (SEM), pHpzc, and Fourier transform infrared spectroscopy (FTIR). The binary complexes of Ln(III) ions with CA at various metal:ligand ratios were investigated using the potentiometric method. The overall stability constants of the complexes were determined.

Green and Short Preparation of CeO2 Nanoparticles with Large Specific Surface Area by Spray Pyrolysis.

Green and short preparation of CeO2 nanoparticles with large specific surface area from rare earth extraction (CeCl3) was successfully achieved by spray pyrolysis (SP). In this method, a precursor solution is first prepared by mixing CeCl3, C6H8O, and H2O in the requisite quantities. Subsequently, the precursor consisting of a mixture of CeO2 and C was obtained by SP method by using the precursor solution. Finally, the calcination at 500 °C~800 °C in air for two hours to transform the precursor to CeO2 nanoparticles. Thermodynamic analysis and experimental studies were performed to determine the optimal SP temperature and citric acid amount. The results indicated that the maximum specific surface area (59.72 m2/g) of CeO2 nanoparticles were obtained when the SP temperature was 650 °C and the molar ratio of citric acid to CeCl3 was 1.5.

The development of Moringa leaves effervescent granules with effervescent agent of citric acid and sodium bicarbonate

Moringa leaves are part of Moringa Oleifera, which have a high antioxidant content, therefore, it is beneficial for overcoming free radicals in the body. Furthermore, the leaves contents have the potential to be developed into a functional drink in the form of effervescent granules. The important aspects influencing the physical characteristics, stability, and acceptability of granule is the type and ratio of the effervescent agent. In this study, citric acid and sodium bicarbonate were used as effervescent agents because they both provide acceptable texture and mouthfeel. This study aimed to develop an effervescent granule formula of Moringa leaves and to optimize the molar ratio of citric acid and sodium bicarbonate as the effervescent agent. Three molar ratios of citric acid and sodium bicarbonate were optimized, namely 1:3.11 (Formulation 1), 1:3 (Formulation 2), and 1:2.93 (Formulation 3). These formulations were developed using the wet granulation method. The results showed effervescent granules of the three formulations exhibited good flowability and uniform particle size distribution. Furthermore, formulation 3 showed better granule flow characteristics than the others. The results after reconstitution showed the granules were quickly dispersed within 207-234 secs, the pH of the preparation ranged between 5.74-5.92 (neutral pH), the viscosity was between 326-333 cps, and exhibited dilatant flow characteristics. Also, the organoleptic and sensory evaluation results showed formulation 3 was the most acceptable in terms of color, taste, aroma, and texture. Based on these findings, it was concluded that formulation 3 which used (citric acid ratio, sodium bicarbonate 1:2.93) was the optimal formulation.