Search Results (117)

Diphenylamine is an important organic chemical intermediate, and its industrial synthesis is mainly achieved through the continuous condensation of aniline. In this study, Hβ zeolite was modified with citric acid, and its catalytic performance in the aniline condensation reaction for diphenylamine synthesis was systematically investigated. The crystal structure, acidic characteristics, pore properties, and Si/Al composition of the catalysts were comprehensively characterized by means of XRD, SEM, BET, Py-IR, ICP, and ²⁷Al MAS NMR. The catalytic activities of Hβ zeolites modified with different concentrations of citric acid were evaluated in a micro fixed-bed reactor, and the structure–activity relationship was systematically discussed in combination with the characterization results. The results demonstrate that the Hβ zeolite modified with 1.5 mol/L citric acid achieves precise matching with the aniline condensation reaction in terms of crystal structure integrity, pore channel parameters, acid property distribution, and Si/Al ratio regulation. Compared with the unmodified catalyst, its catalytic activity is improved by approximately 28%, with a diphenylamine selectivity of 100%. This study proposes a modification mechanism of Hβ zeolite by citric acid. Full article

In this current study, beech wood (Fagus sylvatica) was modified by cross-linking via esterification with combinations of polyethylene glycol (PEG) 400 and various carboxylic acids. Promising combinations (1,2,3,4-butanetetracarboxylic acid (BTCA)/PEG400; citric acid (CA)/PEG400; malic acid (MA)/PEG400) were examined in previous studies. The goal of this study was the optimisation of the treatment. The use of a catalyst, the concentration of the chemicals and the curing conditions were varied. The weight percentage gain (WPG), bulking and anti-swelling efficiency (ASE) after leaching in water were used to evaluate the success of modification. Optimal results were achieved with a curing temperature of 160 °C. Without the addition of PEG, the WPG and bulking values were lower. The use of sodium hypophosphite monohydrate (SHP) as a catalyst had a positive effect only on the combination of BTCA/PEG400. Variations of concentrations usually had a higher impact on WPG and bulking than on ASE. The combination of MA/PEG 400 generally showed lower values. Full article

The citric acid cycle disruptions are implicated in the pathogenesis of chronic diseases, including diabetes, obesity, cancer, and cardiovascular conditions. Numerous publications link TCA cycle disorders to oncological, neurodegenerative, and osteoporotic diseases, and specific single-nucleotide polymorphisms have been proposed as potential markers. Nevertheless, lifestyle and diet have been strongly linked to risk factors for mitochondrial dysfunction; thus, preventive measures that minimize these risks are a relevant field of research. This review summarizes 45 years of relevant publications on the TCA cycle, its genetics and epigenetics, and the restorative potential of certain nutrients. The review includes articles in English and Russian, registered in PubMed, Elsevier, eLIBRARY.RU. The genes encoding the TCA cycle enzymes have been collected and presented. Information is provided that a number of changes in the expression of these genes, for example, Arg18Trp, Ser87Leu, Ala252Thr, and Leu357Val of the ACO2 gene, leads to the development of neurodegenerative diseases; mutations rs121913499, rs121913500 in the IDH1, IDH2 genes, rs1270341616 and the DLST gene lead to the development of cancer. There is evidence that through epigenetic modifications, nutrition affects the activity of the TCA cycle. Niacin, α-lipoic acid, succinic acid, resveratrol, curcumin, arginine, leucine, quercetin, ursolic acid, and alternol affect the regulation of the TCA cycle at the genetic level. Further research into the effects of plant metabolites, vitamins, and bioactive supplements on the TCA cycle may improve the existing preventative and therapeutic diets. Full article

Background/Objectives: Primary metabolic diseases including mitochondrial encephalomyopathies (ME), glycolytic enzymopathies, and disorders of lipid and amino acid metabolism can manifest with severe neurological and neuromuscular symptoms. Conversely, it is increasingly appreciated that primary neurodegenerative diseases can have metabolic etiology and pathophysiology. Pharmacological treatments have limited benefit for these classes of diseases, but dietary therapy is increasingly recognized as a tool for bolstering metabolic processes that can ameliorate neurological symptoms. The ketogenic diet is the best-established example, having long been used as a therapy for epilepsy. Replenishing metabolic intermediates (anaplerosis) especially substrates of the citric acid cycle (CAC) is currently being explored, with ongoing clinical trials of simple metabolic intermediates such as oxaloacetate or NAD+ to treat neurodegenerative diseases. We have shown ketogenic and anaplerotic therapies to be effective in a Drosophila model of ME; however, the full therapeutic potential and role of the CAC in neuronal health is still not well understood. Methods: Here, we have used genetic, behavioral, and dietary approaches to elucidate critical links between the CAC and neurological function. Results: We have found that stimulating the CAC can improve and sustain neurological health in the face of severe metabolic disease, and that its functions include a previously unrecognized role in maintaining normal circadian rhythms, whose disruption is often an early indicator or complicating factor in neurological and neurodegenerative disease. We investigated the hypothesis that the production of GTP by the CAC may be an important mechanistic contributor to the role of the CAC in neurological health and disease, and may underlie its therapeutic potential. Conclusions: Overall, our findings expand our understanding of the role of the CAC in neurological health and disease, support its development as a therapeutic target, and provide a foundation for further studies investigating the intersection between neurological disease and metabolic function. Full article

A carbon-modified attapulgite composite (C-AATP@CTAB) was synthesized via the hydrothermal method using citric acid as the carbon source and cetyltrimethylammonium bromide (CTAB) as a surface modifier for efficient rhodamine B (Rh-B) removal. Carbon modification elevated the composite’s specific surface area (212 m²/g) and negative surface charge (−38.21 mV), significantly enhancing dye adsorption capacity to 666.66 mg/g—nearly double that of unmodified ATP variants (360.4–386.8 mg/g). Kinetic studies confirmed pseudo-second-order adsorption kinetics, attributed to hydrogen bonding and van der Waals interactions between Rh-B and the composite. Under photo-Fenton conditions, C-AATP@CTAB achieved 99.8% Rh-B degradation within 20 min, demonstrating superior catalytic performance in heterogeneous Fenton/photo-Fenton systems. This work establishes a low-cost, high-efficiency adsorbent-catalyst hybrid derived from low-grade attapulgite, offering promising avenues for sustainable wastewater treatment. Full article

Aluminum nitride (AlN) possesses an exceptional combination of high thermal conductivity and an ultra-wide band gap, rendering it highly attractive for electronic packaging and semiconductor substrate applications. In this study, surface chemical modification of AlN powders was performed employing low-molecular-weight organic acids, successfully yielding hydrolysis-resistant AlN powders. The underlying mechanisms responsible for the improved anti-hydrolysis performance imparted by both single organic acids and the composite acid were systematically investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM), characterization techniques. The results reveal that Oxalic acid within the concentration range of 0.25 M to 1.50 M partially inhibits the hydrolysis of aluminum nitride (AlN); however, hydrolysis products such as aluminum hydroxide are still formed. In the case of citric acid, a higher concentration leads to a stronger anti-hydrolysis effect on the modified AlN. No significant hydrolysis products were detected when the AlN sample was treated in a 1 M aqueous citric acid solution at 80 °C. The effectiveness of the organic acids in enhancing the hydrolysis resistance of AlN follows the order: composite acid (citric acid + oxalic acid) > citric acid > oxalic acid. Under the action of the composite acid, the AlN diffraction peaks exhibit the highest intensity. Furthermore, TEM observations reveal the formation of an amorphous protective layer on the surface, which contributes to the improved hydrolysis resistance. Analytical results confirmed that the surface modification process, mediated by citric acid, oxalic acid, or the composite acid, involved an esterification-like reaction between the surface hydroxyl groups on AlN and the chemical modifiers. This reaction led to the formation of a continuous protective coordination layer encapsulating the AlN particles, which serves as an effective diffusion barrier against water molecules, thereby significantly inhibiting the hydrolysis reaction. Full article

Chitosan (CS) and carboxymethyl chitosan (CMCS) are polysaccharides valued for their biocompatibility, reactivity, and film-forming capabilities. This study compares the surface characteristics and stability of CS and CMCS thin films crosslinked with citric acid (CTA), polyethylene glycol diglycidyl ether (PEGDE), and glutaraldehyde (G). Flow behavior was assessed using steady-shear measurements, while film structure, morphology, and physical properties were analyzed by infrared spectroscopy, SEM, AFM, mechanical testing, and swelling experiments. Crosslinking generated new chemical bonds in both CS and CMCS films; however, interactions in CMCS did not result in stable cross-links and were comparatively weaker. These structural modifications influenced swelling behavior and enhanced stability, particularly in CS-based systems. Before neutralization, CS/PEGDE films exhibited the lowest swelling (67% ± 19) relative to unmodified CS (118% ± 25) and crosslinked samples such as CS/G2 (185% ± 30), CS/G1 (475% ± 88), and CS/CTA (520% ± 90). After neutralization, CS/G1 and CS/CTA maintained the highest swelling capacity. In contrast, CMCS films crosslinked with CTA and G1 dissolved rapidly in aqueous media due to high water uptake, while PEGDE- and G2-modified CMCS films demonstrated stability comparable to CS. Overall, the results highlight the superior stability and tunable surface properties of CS-based films, underscoring their potential for biomedical and packaging applications. Full article

This study evaluated the effects of glycerol–citric acid (Gly-CA) modification and polyurethane (PU) adhesive concentration on the properties and termite resistance of rattan skin-based particleboards. Rattan skin particles were modified with 0%, 20%, and 40% Gly-CA and bonded using 6% or 12% PU adhesive. Gly-CA modification significantly improved dimensional stability, reducing water absorption and thickness swelling to about 35–40% and 4–6%, respectively, at 40% Gly-CA with 12% PU. However, excessive modification decreased mechanical strength due to over-crosslinking, while 20% Gly-CA provided the best balance between strength and stability. FTIR analysis confirmed ester and urethane bond formation, while thermogravimetric results showed enhanced thermal stability with increasing Gly-CA content (T_max up to 356.8 °C). Field tests conducted over 98 days revealed a substantial improvement in durability, with termite-induced mass loss decreasing from about 28% in untreated boards to below 8% in Gly-CA–modified samples. From this study, the combination of 40% Gly-CA modification and 12% PU adhesive produced particleboards with improved dimensional and thermal stability, as well as durability against termites. These findings highlight glycerol–citric acid bio-modification as a sustainable and effective strategy for developing durable eco-friendly rattan skin-based composites. Full article

Hybrid membranes are promising alternatives for various applications, combining a continuous polymer phase with a dispersed filler phase to achieve synergistic functional benefits. The ideal fillers should possess well-defined structures and unique properties for multi-functionality, as well as being sourced from renewable, biodegradable materials for sustainability purposes. This study explored the potential of using cellulose-based renewable materials as fillers for hybrid polymer electrolyte membranes (PEMs) in fuel cells. Cellulose whiskers (CWs), known for their high crystallinity and elastic modulus, were effectively synthesized via optimized sequential alkali treatment and acid hydrolysis. Subsequent functionalization with citric acid was performed to enhance their reinforcing properties and overall performance. Initial characterization using ATR-FTIR and XRD confirmed the CWs’ structural composition, high crystallinity, and the presence of reactive groups (sulfate and hydroxyl). The functionalization process introduced new carbonyl groups (C=O), which was verified by ATR-FTIR, while maintaining high hydrophilicity. Morphological analysis revealed that the crosslinked CWs created a denser and more compact microstructure within the membrane, leading to a significant enhancement in mechanical strength. The modifications to the cellulose whiskers not only improved structural integrity but also boosted the membrane’s ion exchange capacity (IEC) and proton conductivity compared to membranes with unmodified CWs. Initial experiments demonstrated CWs’ compatibility as a filler in a polysulfone (PSU) matrix, forming hybrid membranes suitable for fuel cell applications. Full article

The present study serves as a proof-of-concept of our previous work, as the buckwheat (BW) starch film solutions are applied as edible coatings on strawberries and as film packaging materials for strawberry preservation. The BW starch film solution was modified with citric acid (CA) for cross-linking and chitosan nanoparticles (CNP) and by ultrasound application. We tested four formulations for coating: uncoated (negative control), BW starch only (positive control), BW starch with CA and CNP, and ultrasonicated BW starch with CA and CNP. Results demonstrated that BW starch coating, with or without modifications, had positive effects in preserving strawberry quality during 14 days of refrigerated storage at 4 ± 1 °C and 82 ± 1% RH. Coating with only BW starch better suppressed weight loss; a 16% reduction in weight loss was observed compared to the uncoated counterpart at day 14. On the other hand, modifications of coating formulation played a role in preserving different fruit quality parameters. BW starch with CA and CNP had improved textural properties and reduced signs of decay. A 56% reduction in the decay index (DI) was observed in the coated fruits compared to the control. Starch coating restricted chemical changes and maintained total phenolic content (TPC) during storage. TPC in ultrasound-treated solution-coated fruits was the highest, 1.3 mg GAE/g, at the end of the storage. As packaging materials, BW starch films effectively reduced moisture loss from packaged strawberries. The future scope of the study lies in optimizing film solutions for various applications and in understanding enzymatic activities in BW starch-coated fruits. Full article

In this work, we fabricated activated carbon using the peel of musa paradisiaca (banana) as the carbonaceous material source. The activated carbon was obtained after applied a carbonization process under nitrogen atmosphere at 723.15 K. The activated carbon was chemically modified using three chemical agents (citric acid, tartaric acid, and EDTA). The surface properties of the materials were characterized by nitrogen sorptometry at 77 K. Furthermore, we determined the zero-load point of all materials. The kinetic and isothermal behavior of the materials to remove methylene blue from aqueous solution was studied. The thermodynamic parameters of the process for all materials were determined by applying the van’t Hoff equation. Results showed that after chemical activation, there was an increase in the content of oxygenated groups onto activated carbon. Furthermore, the BET surface area of activated carbon was reduced from 808 to 724 m² g⁻¹. The volume of micropores was smaller after chemical activation and the volume of mesopores was greater. The zero-load point of materials was in a range between 4.96 and 5.60. Kinetic and isothermal results showed that after chemical modification, the removal capacity increased from 30.2 for activated carbon to 52.6 mg g⁻¹ for activated carbon modified with EDTA. Finally, the thermodynamic parameters showed that methylene blue adsorption using all materials was an endothermic and spontaneous process; the ΔG° value of activated carbon was −4.35 kJ/mol, and the ΔG° value of activated carbon modified with EDTA was −6.28 kJ/mol. Full article

Incorporating cyclodextrins (CDs) into ionically crosslinked polysaccharide matrices offers a promising strategy for developing well-defined, safe-by-design and biocompatible carrier systems with tunable rheological properties. In this study, β-cyclodextrin (β-CD) was functionalized with citric acid (CDC) and maleic anhydride (CDM) using solvent-free synthesis to improve compatibility with alginate hydrogels. The modified CDs were characterized by FTIR, ¹H NMR, DLS, zeta potential, and MS, confirming successful esterification (4.0 and 3.4 –OH substitution for CDC and CDM, respectively) and stable aqueous dispersion. Rheological measurements showed that native CD accelerated gelation (within approximately 30 s), while CDC and CDM delayed crosslinking (by 2 to 13 min) and reduced gel strength, narrowing the linear viscoelastic range to 0.015–0.089% strain due to competition between polycarboxylated CDs and alginate chains for Ca²⁺ ions. Vibrational prilling produced alginate microbeads with diameters of 800–1000 µm and a simultaneous increase in size and CD concentration. Hydrogels demonstrated high CD retention (>80% after 28 h) and slightly greater release of CDC and CDM than native CD. Overall, solvent-free modification of CDs with citric and maleic acids provides a sustainable approach to tailoring the gelation kinetics, viscoelasticity, and release behavior of alginate-based hydrogels, offering a versatile, food- and health-compliant platform for controlled delivery of bioactive compounds. Full article

This study explores the use of mid-infrared (MIR) free-electron laser (FEL) irradiation as a tool for tailoring the surface properties of electrochemically synthesized TiO₂—graphene quantum dots (QDs). The QDs, prepared in colloidal form via a cost-effective electrochemical method in a KCl—citric acid medium, were exposed to MIR wavelengths (5.76, 8.02, and 9.10 µm) at the Kyoto University FEL facility. Post-irradiation measurements revealed a pronounced inversion of zeta potential by 40–50 mV and approximately 10% reduction in hydrodynamic size, indicating double-layer contraction and ionic redistribution at the QD—solvent interface. Photoluminescence spectra showed enhanced emission for GQDs and TiO₂/GQD composites, while Tauc analysis revealed modest bandgap blue shifts (0.04–0.08 eV), both consistent with trap-state passivation and sharper band edges. TEM confirmed intact crystalline structures, verifying that FEL-induced modifications were confined to surface chemistry rather than bulk lattice damage. Taken together, these results demonstrate that MIR FEL irradiation provides a resonance-driven, non-contact method to reorganize ions, suppress defect states, and improve the optoelectronic quality of QDs. This approach offers a scalable post-synthetic pathway for enhancing electron transport layers in perovskite solar cells and highlights the broader potential of photonic infrastructure for advanced nanomaterial processing and interface engineering in optoelectronic and energy applications. Full article

Rare earth elements (REEs) make up integral components in personal electronics, healthcare instrumentation, and modern energy technologies. REE leaching with organic acids is an environmentally friendly alternative to traditional extraction methods. Our previous study demonstrated that batch ultrasound-assisted organic acid leaching of REEs can significantly decrease environmental impacts compared to traditional bioleaching. The batch method is limited to small volumes and is unsuitable for industrial implementation. This study proposes a novel approach to increase reaction volume using a continuous ultrasound-assisted organic acid leaching method. Laboratory experiments showed that continuous ultrasound-assisted leaching increased the leaching rate (µg/h) 11.3–24.5 times compared to our previously reported batch method. Techno-economic analysis estimates the cost of the continuous approach using commercially purchased organic acids is $9465/kg of extracted REEs and $4325/kg of extracted REEs, using gluconic acid and citric acid, respectively. The sensitivity analysis reveals that substituting commercially purchased organic acids with microbially produced biolixiviant can reduce the process cost by approximately 99% while minimally increasing energy consumption. Environmental assessment shows that most of the emissions stemmed from the energy required to power the ultrasound reactor. We concluded that increased leaching capacity using a continuous ultrasound-assisted approach is feasible, but process modifications are needed to reduce the environmental impact. Full article

Protein palmitoylation, a key post-translational modification (PTM) regulating protein transport and function, is catalyzed by palmitoyl transferases (PATs). PATs play vital roles in plant growth, development, and stress responses, yet their characterization in citrus remains limited. This study identified 23 PAT genes (CitPATs) possessing the conserved DHHC domain in the citrus genome through comprehensive genome-wide analysis. Analysis revealed that most CitPAT proteins are hydrophilic, basic, and stable, with significant variations in sequence length. Gene structure and motif analysis confirmed 10 conserved motifs, with the DHHC domain being the most conserved among all 23 members. The CitPAT genes were unevenly distributed across nine chromosomes and exhibit high evolutionary conservation. Promoter analysis identified numerous cis-acting elements associated with abiotic stress and hormone responses, including basic regulatory elements, light-responsive elements, and stress-responsive elements, with light-responsive elements being predominant. Expression profiling during fruit development revealed distinct correlation patterns with citric acid dynamics: CitPAT6, CitPAT18, and CitPAT23 showed positive correlations with acid accumulation, while CitPAT1, CitPAT10, and CitPAT13 exhibited negative correlations. Further RT-qPCR experiments revealed that CitPAT1 and CitPAT10 consistently demonstrated strong negative correlations with citrate content throughout fruit development. This functional diversification suggests roles in regulating citric acid metabolism. These findings provide novel insights into quality formation in facility-cultivated citrus and establish a foundation for understanding PAT-mediated regulation of fruit development. Full article