Search Results (90)

An anion exchange-assisted technique was used for the synthesis of platinum-decorated SnO₂ supports, providing nanocatalysts with enhanced activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In this study, a series of SnO₂ supports, namely SnA (synthesized almost at room temperature), SnB (hydrothermally treated at 180 °C), and SnC (annealed at 600 °C), are systematically investigated, all loaded with 1 mol% Pt from H₂PtCl₆ under identical mild conditions. The chloride ions from the SnCl₄ precursors were efficiently removed via a strong-base anion exchange reaction, resulting in highly dispersed, crystalline ~5 nm cassiterite SnO₂ particles. All Pt/SnO₂ composites displayed mesoporous structures with type IVa isotherms and H₂-type hysteresis, with SP1a (Pt on SnA) exhibiting the largest surface area (122.6 m²/g) and the smallest pores (~3.5 nm). STEM-HAADF imaging revealed well-dispersed PtOx domains (~0.85 nm), while XPS confirmed the dominant Pt⁴⁺ and Pt²⁺ species, with ~25% Pt⁰ likely resulting from photoreduction and/or interactions with Sn–OH surface groups. Raman spectroscopy revealed three new bands (260–360 cm⁻¹) that were clearly visible in the sample with 10 mol% Pt and were due to the vibrational modes of the PtOx species and Pt-Cl bonds introduced due the addition and hydrolysis of H₂PtCl₆ precursor. TGA/DSC analysis revealed the highest mass loss for SP1a (~7.3%), confirming the strong hydration of the PtOx domains. Despite the predominance of oxidized PtOx species, SP1a exhibited the highest catalytic activity (k_app = 1.27 × 10⁻² s⁻¹) and retained 84.5% activity for the reduction of 4-NP to 4-AP after 10 cycles. This chloride-free low-temperature synthesis route offers a promising and generalizable strategy for the preparation of noble metal-based nanocatalysts on oxide supports with high catalytic activity and reusability. Full article

Vitamins are crucial micro-nutrients for overall well-being, making continuous monitoring essential. There are demands to provide an alternative detection, especially using a portable detection or a point-of-care-testing (POCT) device. One promising approach is employing an in situ electro-polymerised MIP (eMIP), which offers a straightforward polymerisation technique on screen-printed electrodes (SPEs). Here, we report a review based on three databases (PubMed, Scopus, and Web of Science) from 2014 to 2024 using medical subject heading (MeSH) terms “electrochemical polymerisation” OR “electropolymerisation” crossed with the terms “molecularly imprinted polymer” AND “vitamin A” OR “vitamin D” OR “vitamin E” OR “vitamin K” OR “fat soluble vitamin” OR “vitamin B” OR “vitamin C” OR “water soluble vitamin”. The resulting 12 articles covered the detection of vitamins in ascorbic acid, riboflavin, cholecalciferol, calcifediol, and menadione using monomers of catechol (CAT), 3,4-ethylenedioxythiophene (EDOT), o-aminophenol (oAP), o-phenylenediamine (oPD), pyrrole, p-aminophenol (pAP), p-phenylenediamine (pPD), or resorcinol (RES), using common bare electrodes including graphite rod electrode (GRE), glassy carbon electrode (GCE), gold electrode (GE), and screen-printed carbon electrode (SPCE). The most common electrochemical detections were differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV). The imprinting factor (IF) of the eMIP-modified electrodes were from 1.6 to 21.0, whereas the cross-reactivity was from 0.0% to 29.9%. Several types of food and biological samples were tested, such as supplement tablets, poultry and pharmaceutical drugs, soft drinks, beverages, milk, infant formula, human and calf serum, and human plasma. However, more discoveries and development of detection methods needs to be performed, especially for the vitamins that have not been studied yet. This will allow the improvement in the application of eMIPs on portable-based detection and POCT devices. Full article

Designing conducting polymers with novel structures is essential for electrochemical energy storage devices. Here, copolymers of s-triazine and o-aminophenol are electropolymerized from an aqueous solution onto a carbon cloth substrate using the galvanostatic method. The poly(s-triazine-co-o-aminophenol) (PT-co-oAP) is characterized, and its charge storage properties are investigated in 1 M H₂SO₄ and in 1 M ZnSO₄. At 1 A g⁻¹, the specific capacities of PT-co-oAP reach 101.3 mAh g⁻¹ and 84.4 mAh g⁻¹ in 1 M H₂SO₄ and in 1 M ZnSO₄, respectively. The specific capacity of PT-co-oAP maintains 90.3% of its initial value after cycling at 10 A g⁻¹ for 2000 cycles in 1 M H₂SO₄. The high specific capacity achieved originates from abundant surface active sites, facile ion diffusion, with optimized active site structure achieved by forming copolymer. The charge storage mechanism involves the redox processes of amino/imino groups and hydroxyl/carbonyl groups in the copolymer, together with the insertion of cations. Two electrode devices using two PT-co-oAP and aqueous 1 M H₂SO₄ are assembled, and the maximum energy density reaches 63 Wh kg⁻¹ at 0.5 A g⁻¹ with a power density of 540 W kg⁻¹. The capacity retention of the device after 3000 cycles at 10 A g⁻¹ reaches 81.2%. Full article

We report a method for the synthesis of 2-substituted benzoxazoles from tertiary amides and 2-aminophenols in the presence of triflic anhydride (Tf₂O) and 2-Fluoropyridine (2-F-Pyr). The cascade reaction involves the activation of the amide carbonyl group by Tf₂O, nucleophilic addition, intramolecular cyclization, and elimination. Furthermore, we explore the scope of this method by varying both the amide and 2-aminophenol substrates, highlighting its versatility in the synthesis of a wide range of functionalized benzoxazole derivatives. Full article

The availability of water-soluble nanoparticles allows catalytic reactions to occur in highly desirable green environments. The catalytic activity and selectivity of water-soluble palladium nanoparticles capped with 6-(carboxylate)hexanethiolate (C6-PdNP) and 5-(trimethylammonio)pentanethiolate (C5-PdNP) were investigated for the reduction of 4-nitrophenol, the oxidation of α,β-conjugated aldehydes, and the C-C coupling of phenylboronic acid. The study showed that between the two PdNPs, C6-PdNP exhibits better catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride and the selective oxidation of conjugated aldehydes to conjugated carboxylic acids. For the latter reaction, molecular hydrogen (H₂) and H₂O act as oxidants for the surface palladium atoms on PdNPs and conjugated aldehyde substrates, respectively. The results indicated that the competing addition activities of Pd-H and H₂O toward the π-bond of different unsaturated substrates promote either reduction or oxidation reactions under mild conditions in organic solvent-free environments. In comparison, C5-PdNP exhibited higher catalytic activity for the C-C coupling of phenylboronic acid. Gas chromatography–mass spectrometry (GC-MS) was mainly used as an analytical technique to examine the products of catalytic reactions. Full article

The reduction of unfriendly 4-nitrophenol to make it unimpactful with the environment (4-aminophenol) was carried out using the metastable form of copper ferrite (CuFe₅O₈) synthesized by the co-precipitation of metal nitrate salts, an efficient method with inexpensive and abundant starting materials. The samples were obtained by calcination at various temperatures ranging from 600 °C to 900 °C. The material characterizations, including X-ray diffraction, N₂ adsorption/desorption, scanning electron microscope, X-ray absorption spectroscopy, and ultraviolet–visible spectrometry, were employed to identify the detailed structures and describe their correlations with catalytic activities. The X-ray diffraction and X-ray absorption spectroscopy analyses revealed the presence of mixed CuFe₅O₈ and copper oxide phases, where the formers are rich in Cu²⁺, Fe²⁺, and Fe³⁺ ions. The electron transfer between Cu²⁺, Fe²⁺, and Fe³⁺ led to the high efficiency of the catalytic reaction of the synthesized copper ferrites. Especially for the sample calcined at 600 °C, the apparent kinetic constant (k) for a reduction of 4-nitrophenol was equal to 0.25 min⁻¹, illustrating nearly 100% conversion of 4-nitrophenol to 4-aminophenol within less than 9 min. Regarding the N₂ adsorption/desorption isotherms, the samples calcined at 600 °C have the highest specific Brunauer–Emmett–Teller (BET) surface area (15.93 m² g⁻¹) among the others in the series, which may imply the most effective catalytic performance investigated herein. The post-catalytic X-ray diffraction investigation indicated the stability of the prepared catalysts. Furthermore, the chemical stability of the prepared catalysts was confirmed by its reusability in five consecutive cycles. Full article

Emerging pollutants, such as N-acetyl-para-aminophenol, pose significant challenges to environmental sustainability, and Bi₂Fe₂O₂ (BFO) nanomaterials are an emerging class of piezoelectric materials. This study presents a novel piezoelectric-driven Fenton system based on Bi₂Fe₄O₉ nanosheets for the efficient degradation of organic pollutants. BFO nanosheets with varying thicknesses were synthesized, and their piezoelectric properties were confirmed through piezoresponse force microscopy and heavy metal ion reduction experiments. The piezoelectric electrons generated within the BFO nanosheets facilitate the in situ production of hydrogen peroxide, which in turn drives the Fenton-like reaction. Furthermore, the piezoelectric electrons enhance the redox cycling of iron in the Fenton process, boosting the overall catalytic efficiency. The energy band structure of BFO nanosheets is well-suited for this process, enabling efficient hydrogen peroxide generation and promoting Fe³⁺ reduction. The findings demonstrate that thinner BFO nanosheets exhibit superior piezoelectric activity, leading to enhanced catalytic performance. Additionally, the incorporation of gold nanodots onto BFO nanosheets further boosts their piezocatalytic efficiency, particularly in the reduction of Cr (VI). The system exhibited robust oxidative capacity, stability, and recyclability, with reactive oxygen species (ROS) verified via electron paramagnetic resonance spectroscopy. Overall, BFO nanosheets, with their optimal energy band structure, self-supplied hydrogen peroxide, and enhanced Fe³⁺ reduction, represent a promising, sustainable solution for advanced oxidation processes in wastewater treatment and other applications. Full article

A series of new quinazolin-2,4-dione derivatives incorporating amide/eight-membered nitrogen-heterocycles 2a–c, in addition, acylthiourea/amide/dithiolan-4-one and/or phenylthiazolidin-4-one 3a–d and 4a–d. The starting compound 1 was prepared by reaction of 4-(2,4-dioxo-1,4-dihydro-2H-quinazolin-3-yl)-benzoyl chloride with ammonium thiocyanate and cyanoacetic acid hydrazide. The reaction of 1 with strong electrophiles, namely, o-aminophenol, o-amino thiophenol, and/or o-phenylene diamine, resulted in corresponding quinazolin-2,4-dione derivatives incorporating eight-membered nitrogen-heterocycles 2a–d. Compounds 3a–d and 4a–d were synthesized in good-to-excellent yield through a one-pot multi-component reaction (MCR) of 1 with carbon disulfide and/or phenyl isocyanate under mild alkaline conditions, followed by ethyl chloroacetate, ethyl iodide, methyl iodide, and/or concentrated HCl, respectively. The obtained products were physicochemically characterized by melting points, elemental analysis, and spectroscopic techniques, such as FT-IR, ¹H-NMR, ¹³C-NMR, and MS. The antibacterial efficacy of the obtained eleven molecules was examined in vitro against two Gram-positive bacterial strains (Staphylococcus aureus and Staphylococcus haemolyticus). Furthermore, Computer-Aided Drug Design (CADD) was performed on the synthesized derivatives, standard drug (Methotrexate), and reported antibacterial drug with the target enzymes of bacterial strains (S. aureus and S. haemolyticus) to explain their binding mode of actions. Notably, our findings highlight compounds 2b and 2c as showing both the best antibacterial activity and docking scores against the targets. Finally, according to ADMET predictions, compounds 2b and 2c possessed acceptable pharmacokinetics properties and drug-likeness properties. Full article

Yearly, thousands of tons of wasted coffee grounds are produced according to high coffee consumption. Still, after the coffee brewing, wasted coffee grounds contain some amounts of caffeine (CAF). CAF, in turn, contains multiple O and N chelating atoms in its structure. These have a potential to be reductors for complexes of metals. In this context, within the present study, a set of CAF extracts derived from coffee beans and coffee grounds were obtained and then used for the one-step reduction of ReO₄⁻ ions with no additional toxic chemicals. Within this approach, CAF was applied as a secondary, green resource for the synthesis of unique rhenium nanoparticles (ReNPs) containing Re species at 0 and +6 oxidation states. The obtained ReNPs were identified and characterized with the use of X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Further, the capping and stabilization of ReNPs by CAF were verified with the aid of Fourier transformation infrared spectroscopy (FT-IR). The so-obtained “green” ReNPs were then used as a homogenous catalyst in the catalytic hydrogenation of 4-nitrophenol (4-NP). This new nanomaterial revealed a superior catalytic activity, leading to the complete reduction of 4-NP to 4-aminophenol within 40–60 min with a first-order rate constant of 0.255 min⁻¹. Full article

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO₂ and TiO₂ supports on reaction dynamics using NaBD₄ were studied and focused on the relative yields of [HD]/[H₂] and [D₂]/[H₂]. The findings show a consistent increase in HD yields with rising [BD₄⁻] concentrations. Notably, the sequence of HD yield enhancement follows the order of TiO₂-Au⁰-NPs < Au⁰-NPs < SiO₂-Au⁰-NPs. Conversely, the rate of H₂ evolution during BH₄^- hydrolysis exhibits an inverse trend, with TiO₂-Au⁰-NPs outperforming the others, followed by Au⁰-NPs and SiO₂-Au⁰-NPs, demonstrating the opposing effects exerted by the TiO₂ and SiO₂ supports on the catalytic processes. Further, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) confirms the catalytic mechanism, with TiO₂-Au⁰-NPs demonstrating superior activity. The catalytic activity observed aligns with the order of TiO₂-Au⁰-NPs > Au⁰-NPs > SiO₂-Au⁰-NPs, suggesting that SiO₂ donates electrons to Au⁰-NPs, while TiO₂ withdraws them. It is of interest to note that two very different processes, that clearly proceed via different mechanisms, are affected similarly by the supports. This study reveals that the choice of support material influences catalytic activity, impacting overall yield and efficiency. These findings underscore the importance of selecting appropriate support materials for tailored catalytic outcomes. Full article

The ever-increasing expansion of chemical industries produces a variety of common pollutants, including colors, which become a global and environmental problem. Using a nanocatalyst is one of the effective ways to reduce these organic contaminants. With this in mind, a straightforward and effective method for the production of a novel nanocatalyst based on lignin-derived carbon, titanium dioxide nanoparticles, and Ag particles (TiO₂/C/Ag) is described. The preparation of carbon and Ag particles (in sub-micro and nano size) was carried out by laser ablation in air. The nanocomposite was synthesized using a facile magnetic stirrer of TiO₂, C, and Ag. According to characterization methods, a carbon nanostructure was successfully synthesized through the laser irradiation of lignin. According to scanning electron microscope images, spherical Ag particles were agglomerated over the nanocomposite. The catalytic activities of the TiO₂/C/Ag nanocomposite were tested for the decolorization of methylene blue (MB) and Congo red (CR), employing NaBH₄ in a water-based solution at 25 °C. After adding fresh NaBH₄ to the mixture of nanocomposite and dyes, both UV absorption peaks of MB and CR completely disappeared after 10 s and 4 min, respectively. The catalytic activity of the TiO₂/C/Ag nanocomposite was also examined for the reduction of 4-nitrophenol (4-NP) using a NaBH₄ reducing agent, suggesting the complete reduction of 4-NP to 4-aminophenol (4-AP) after 2.30 min. This shows excellent catalytic behavior of the prepared nanocomposite in the reduction of organic pollutants. Full article

Baijiu is an ancient, distilled spirit with a complicated brewing process, unique taste, and rich trace components. These trace components play a decisive role in the aroma, taste, and especially the quality of baijiu. In this paper, the redox reaction between the Fenton reagent and four reducing agents, including o-phenylenediamine (OPD), p-phenylenediamine (PPD), 4-aminophenol (PAP), and 2-aminophenol (OAP), was adopted to construct a four-channel visual sensor array for the rapid detection of nine kinds of common organic acids in baijiu and the identification of baijiu and its adulteration. By exploiting the color-changing fingerprint response brought by organic acids, each organic acid could be analyzed accurately when combined with an optimized variable-weighted least-squares support vector machine based on a particle swarm optimization (PSO-VWLS-SVM) model. What is more, this novel sensor also could achieve accurate semi-quantitative analysis of the mixed organic acid samples via partial least squares discriminant analysis (PLSDA). Most importantly, the sensor array could be further used for the identification of baijiu with different species through the PLSDA model and the adulteration assessment with the one-class partial least squares (OCPLS) model simultaneously. Full article

A new iron(III) complex (Et₃NH)₂[Fe(L)₂](ClO₄)·MeOH (1) where H₂L = 2-{(E)-[2-hydroxyphenyl)imino]methyl}phenol has been synthesised and characterised by single crystal XRD, elemental analysis and DC magnetic susceptibility measurements. The dianionic ligands L²⁻ coordinate in a tridentate fashion with the Fe(III) through their deprotonated phenolic oxygens and azomethine nitrogen atoms, resulting in a trans-FeO₄N₂ chromophore. Variable-temperature magnetic measurements were performed between 300 and 5 K under an applied field of 0.1 T and show that 1 is in the high spin state (S = 5/2) over the whole measured temperature range. This is confirmed by Mössbauer spectroscopy at 77 and 300 K. Full article

Herein, chemometric-assisted synthesis of electrochemical sensors based on electropolymerised ion-imprinted polymeric (e-IIP) films was explored. Co(II)-IIPs sensors were prepared by performing electropolymerisation procedures of polymerisation mixtures comprising varying concentrations of an electroactive o-aminophenol (o-AP) monomer and Co(II) ions, respectively, according to the Taguchi L9 experimental design, exploiting the simultaneous evaluation of other controlled parameters during electrosynthesis. Each e-IIP developed from Taguchi runs was compared with the respective non-imprinted polymer (NIP) films and fitted according to Langmuir–Freudlich isotherms. Distinctive patterns of low and high-affinity films were screened based on the qualities and properties of the developed IIPs in terms of binding kinetics (KD), imprinting factor, and the heterogeneity index of produced cavities. These results can provide a generic protocol for chemometric-assisted synthesis of e-IIPs based on poly-o-AP, providing highly stable, reproducible, and high-affinity imprinted polymeric films for monitoring purposes. Full article

Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH₂-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn₁₃ and Pt₃Zn₁₀ in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn₁₃ and Pt₃Zn₁₀ catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn₁₃ and Pt₃Zn₁₀ could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn. Full article