Chemistry

20 pages, 2914 KB

Open AccessArticle

Solvent-Dependent Stabilization of Gold Nanoparticles: A Comparative Study on Polymers and the Influence of Their Molecular Weight in Water and Ethanol

by Marilyn Kaul, Rolf Lennart Vanselow, Ahmed Y. Sanin, Ulf D. Kahlert and Christoph Janiak

Chemistry 2025, 7(5), 159; https://doi.org/10.3390/chemistry7050159 - 1 Oct 2025

Abstract

Gold nanoparticles (AuNPs) are attracting more and more attention in life sciences, especially due to their versatile physicochemical properties whereby their colloidal stability in water and organic solvents is crucial. In this study, a systematic comparison of different polymers, synthesis methods and solvents [...] Read more.

Gold nanoparticles (AuNPs) are attracting more and more attention in life sciences, especially due to their versatile physicochemical properties whereby their colloidal stability in water and organic solvents is crucial. In this study, a systematic comparison of different polymers, synthesis methods and solvents was carried out. The AuNPs were synthesized using the ligand exchange reaction/postsynthetic addition reaction (PAR) and the one-pot synthesis with the polymers poly(vinyl alcohol) (PVA), poly(ethylene glycol) (PEG), poly(vinylpyrrolidone) (PVP) and poly(acrylic acid) (PAA), each with different molar weight averages. Analysis of the AuNP@Polymer conjugates by transmission electron microscopy (TEM) finds essentially unchanged gold nanoparticle core sizes of 11–18 or 11–19 nm in water and ethanol, respectively. The hydrodynamic diameter from dynamic light scattering (DLS) lies largely in the range from 20 to 70 nm and ultraviolet-visible spectroscopy (UV-Vis) showed gold plasmon resonance band maxima between 517 and 531 nm over both synthesis methods and solvents for most samples. The polymer PVA showed the best colloidal stability in both synthesis methods, both in water and after transfer to ethanol. An increased instability in ethanol could only be noted for the PEG coated samples. For the polymers PVP and PAA, the stability depended more specifically on the combination of synthesis method, polymer molecular weight and solvent. Full article

(This article belongs to the Section Chemistry at the Nanoscale)

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17 pages, 4348 KB

Open AccessArticle

[1,2,5]Oxadiazolo[3,4-b]dithieno[2,3-f:2′,3′-h]quinoxaline as a Versatile Scaffold for the Construction of Various Polycyclic Systems as Potential Organic Semiconductors

by Elizaveta M. Krynina, Yuriy A. Kvashnin, Ekaterina F. Zhilina, Denis A. Gazizov, Pavel A. Slepukhin, Gennady L. Rusinov, Egor V. Verbitskiy and Valery N. Charushin

Chemistry 2025, 7(5), 158; https://doi.org/10.3390/chemistry7050158 - 1 Oct 2025

Abstract

A straightforward synthetic method is advanced to produce hard-to-reach polycyclic compounds belonging to the [1,2,5]oxadiazolo[3,4-b]quinoxaline ring system. This approach draws on a combination of the nucleophilic aromatic substitution of hydrogen (S_N^H) and Scholl cross-coupling reactions, followed by reduction [...] Read more.

A straightforward synthetic method is advanced to produce hard-to-reach polycyclic compounds belonging to the [1,2,5]oxadiazolo[3,4-b]quinoxaline ring system. This approach draws on a combination of the nucleophilic aromatic substitution of hydrogen (S_N^H) and Scholl cross-coupling reactions, followed by reduction of the 1,2,5-oxadiazole fragment under mild reaction conditions. All compounds were obtained for the first time with moderate to excellent yields. Electrochemical and photophysical measurements show that the synthesized compounds may serve as narrow-band n-type organic semiconductors, with energy levels ranging from 2.00 to 2.28 eV, comparable to those of the best commercially available electronic semiconductors. Full article

(This article belongs to the Special Issue Oxygen-Containing Heterocyclic Compounds: Recent Advances in Chemistry)

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14 pages, 3208 KB

Open AccessArticle

Coordination Chemistry of Polynitriles, Part XIII: Influence of 4,4′-Bipyridine on the Crystal and Molecular Structures of Alkali Metal Pentacyanocyclopentadienides

by Patrick R. Nimax and Karlheinz Sünkel

Chemistry 2025, 7(5), 157; https://doi.org/10.3390/chemistry7050157 - 1 Oct 2025

Abstract

The reaction of 4,4′-bipyridine (C₁₀H₈N₂) with the alkali metal pentacyanocyclopentadienides [Na{C₅(CN)₅}(MeOH)] and [KC₅(CN)₅] gives the coordination polymers [Na{C₅(CN)₅}(EtOH)(H₂O)(C₁₀H₈N₂ [...] Read more.

The reaction of 4,4′-bipyridine (C₁₀H₈N₂) with the alkali metal pentacyanocyclopentadienides [Na{C₅(CN)₅}(MeOH)] and [KC₅(CN)₅] gives the coordination polymers [Na{C₅(CN)₅}(EtOH)(H₂O)(C₁₀H₈N₂)] (1) and [K{C₅(CN)₅}(H₂O)₂] • 2 (C₁₀H₈N₂) (2) after recrystallization from EtOH. Both compounds show octahedral coordination around the metal ion with a NaN₄O₂ and KN₂O₄ environment. The [C₅(CN)₅] acts as a 1,1-bridging ligand in 1 and a 1,2-bridging ligand in 2. The 4,4′-bipyridine acts as a N,N′-bridging ligand between dimeric [Na₂(EtOH)₂(H₂O)₂(µ-{C₅(CN)₅}₂] units, while it acts only as a guest molecule in the voids between polymeric [K(µ-H₂O)_4/2{µ-C₅(CN)₅}_2/2]_∞ chains. Both compounds employ multiple hydrogen bonds and π stacking to stabilize the crystalline structures. Full article

(This article belongs to the Section Inorganic and Solid State Chemistry)

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22 pages, 4674 KB

Open AccessArticle

Fe₃O₄/Poly(acrylic acid) Composite Hydrogel for the Removal of Methylene Blue and Crystal Violet from Aqueous Media

by Fiorela Ccoyo Ore, Flor de Liss Meza López, Ana Cecilia Valderrama Negrón and Michael Azael Ludeña Huaman

Chemistry 2025, 7(5), 156; https://doi.org/10.3390/chemistry7050156 - 26 Sep 2025

Abstract

An increase in the production of cationic dyes is expected over the next decade, which will have an impact on health and the environment. This work reports an adsorbent hydrogel composed of poly(acrylic acid) [poly(AA)] and Fe₃O₄ particles, prepared by [...] Read more.

An increase in the production of cationic dyes is expected over the next decade, which will have an impact on health and the environment. This work reports an adsorbent hydrogel composed of poly(acrylic acid) [poly(AA)] and Fe₃O₄ particles, prepared by radical polymerization and in situ co-precipitation of Fe³⁺ and Fe²⁺. This Fe₃O₄/poly(AA) composite hydrogel was used to evaluate its potential for removing the cationic dyes methylene blue (MB) and crystal violet (CV) from aqueous solutions. Instrumental characterization of the hydrogel was performed by FTIR, XRD, TGA, VSM, and physicochemical analysis (swelling and response to changes in pH). The results show that the incorporation of Fe₃O₄ particles improves the adsorption capacity of MB and CV dyes to a maximum adsorption of 571 and 321 mg/g, respectively, under the best conditions (pH 6.8, dose 1 g/L, time 24 h). The adsorption data best fit the pseudo-first order (PFO) kinetic model and the Freundlich isothermal model, indicating mass transfer via internal and/or external diffusion and active sites with different adsorption potentials. Moreover, the thermodynamic analysis confirmed that the adsorption process was spontaneous and exothermic, with physisorption as the dominant mechanism. In addition, the Fe₃O₄/poly(AA) hydrogel is capable of removing 95% of the dyes after ten consecutive adsorption–desorption cycles, demonstrating the potential of hydrogels loaded with Fe₃O₄ particles for the treatment of wastewater contaminated with dyes. Full article

(This article belongs to the Section Catalysis)

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13 pages, 2981 KB

Open AccessArticle

On the Selective Conversion of Methane to Methanol Facilitated by Coordinatively Unsaturated Transition Metal Complexes

by Debora P. Vasconcelos and Evangelos Miliordos

Chemistry 2025, 7(5), 155; https://doi.org/10.3390/chemistry7050155 - 26 Sep 2025

Abstract

Density functional theory calculations are performed to examine the reactivity of the coordinatively unsaturated (NH₃)₄RhO²⁺, (NH₃)₄CoO²⁺, and (NH₃)₄FeO⁺ species with methane and methanol. The ground low-spin [...] Read more.

Density functional theory calculations are performed to examine the reactivity of the coordinatively unsaturated (NH₃)₄RhO²⁺, (NH₃)₄CoO²⁺, and (NH₃)₄FeO⁺ species with methane and methanol. The ground low-spin state of rhodium oxide provides ideal energetics for the efficient and selective conversion of methane to methanol. The small activation energy barriers for all three steps (H₃C-H activation, CH₃-OH recombination, oxygen reload) promise fast conversion, while the larger activation barrier for the C-H activation of methanol provides the means to kinetically hinder further oxidation to the thermodynamically more favorable formaldehyde. The key finding was that rhodium prefers the 2 + 2 (as opposed to radical) activation mechanism of methane. To maintain the “ideal” electronic structure observed for (NH₃)₄RhO²⁺, we first replaced rhodium with its first-row lower cost counterpart cobalt. The cobalt complex favors a quartet state, which prefers a radical mechanism leading to the formation of methyl radical. This undesired effect vanishes, switching from Co⁴⁺ to Fe³⁺. Possible explanations for the observed trends are provided in terms of electronic structure features of the three metals. The production of methanol from methane has been a topic of intense interest over the past decades and we believe that this work offers new insights for tackling this challenging problem. Full article

(This article belongs to the Section Theoretical and Computational Chemistry)

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18 pages, 5739 KB

Open AccessArticle

Highly Active and Water-Resistant Mn-Loaded MgAlO_x Catalysts for NH₃-SCR at Low Temperature

by Ruolan Jiang, Ben Wang, Wei Liu, Jian Zhang, Liguo Wang and Zhongpeng Wang

Chemistry 2025, 7(5), 154; https://doi.org/10.3390/chemistry7050154 - 23 Sep 2025

Abstract

Advancing catalysts for low-temperature NH₃-SCR enhances their viability as a terminal flue gas denitration solution across diverse operating regimes. A high-performance, hydrothermally stable catalyst for low-temperature SCR was synthesized by depositing MnO_x onto MgAlO_x composite oxide supports. These supports, [...] Read more.

Advancing catalysts for low-temperature NH₃-SCR enhances their viability as a terminal flue gas denitration solution across diverse operating regimes. A high-performance, hydrothermally stable catalyst for low-temperature SCR was synthesized by depositing MnO_x onto MgAlO_x composite oxide supports. These supports, featuring varied Mg/Al ratios, originated from layered double hydroxide (LDH) precursors. The obtained catalyst with the Mg/Al ratio of 2 (Mn/Mg₂AlO_x) possesses relatively high concentrations of active oxygen species (O_α) and Mn⁴⁺ and exhibits remarkable catalytic performance. The Mn/Mg₂AlO_x catalyst exhibits a wide operating temperature range (100–300 °C) for denitration, achieving over 80% NO_x conversion, along with robust water resistance. The temperature-programed surface reactions and NO oxidation reactions are performed to elucidate the promoting effect of water on N₂ selectivity, which is not only due to inhibition of catalyst oxidation capacity at high temperature but also is related to the competing adsorption of water and NH₃. In situ DRIFTS analysis confirmed that the NH₃-SCR mechanism over Mn/Mg₂AlO_x adheres to the Eley–Rideal (E–R) pathway. These findings highlight the significant promise of Mn/MgAlO_x catalysts for deployment as downstream denitration units within exhaust treatment systems. Full article

(This article belongs to the Special Issue Design and Synthesis of Next-Generation Catalysts for Efficient Green Chemical Reactions)

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34 pages, 7147 KB

Open AccessReview

A Brief Review of Cu-Based Catalysts for the Selective Liquid-Phase Hydrogenation of Furfural to Furfuryl Alcohol

by Tiantian Lin, Yongzhen Gao, Chao Li, Meng Zhang and Zhongyi Liu

Chemistry 2025, 7(5), 153; https://doi.org/10.3390/chemistry7050153 - 22 Sep 2025

Abstract

With the rapid industrialization, excessive reliance on fossil fuels has resulted in energy crises and environmental pollution, driving the search for sustainable alternatives. Biomass-derived resources have emerged as promising candidates to replace fossil-based feedstocks. Among these, furfural (FF) serves as a key platform [...] Read more.

With the rapid industrialization, excessive reliance on fossil fuels has resulted in energy crises and environmental pollution, driving the search for sustainable alternatives. Biomass-derived resources have emerged as promising candidates to replace fossil-based feedstocks. Among these, furfural (FF) serves as a key platform molecule that can be catalytically hydrogenated to various high-value chemicals, with furfuryl alcohol (FA) representing one of the most valuable products. Currently, Cr-based catalysts remain predominant for the selective hydrogenation of FF to FA. However, the severe environmental toxicity of Cr necessitates urgent development of alternative Cr-free catalytic systems. This study systematically reviews recent advances in FF hydrogenation to FA, providing an in-depth discussion of reaction mechanisms, including adsorption configurations, solvent effects, and side reactions, as well as a comprehensive analysis of structure–activity relationships, involving active metal, support, promoter, and preparation methods. Furthermore, we evaluate the application of the advanced characterization techniques for monitoring the reaction processes. Finally, we propose the future research directions: (1) designing efficient and stable non-noble metal catalysts and (2) elucidating reaction mechanisms via the combined in situ characterization and theoretical calculations. These efforts would facilitate the academic understanding and industrial implementation of the FF-to-FA conversion process. Full article

(This article belongs to the Special Issue Catalytic Conversion of Biomass and Its Derivatives)

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11 pages, 1849 KB

Open AccessArticle

Theoretical Study on the Electronic Structure of Fe(0)–, Pd(0)–, and Pt(0)–Phosphine–Carbon Dioxide Complexes

by Tímea R. Kégl and Tamás Kégl

Chemistry 2025, 7(5), 152; https://doi.org/10.3390/chemistry7050152 - 22 Sep 2025

Abstract

The activation of carbon dioxide by transition metal complexes is a fundamental process in catalysis and carbon capture. In this study, density functional theory (DFT) calculations, combined with Quantum Theory of Atoms in Molecules (QTAIM) and Natural Orbitals for Chemical Valency (NOCV) analyses, [...] Read more.

The activation of carbon dioxide by transition metal complexes is a fundamental process in catalysis and carbon capture. In this study, density functional theory (DFT) calculations, combined with Quantum Theory of Atoms in Molecules (QTAIM) and Natural Orbitals for Chemical Valency (NOCV) analyses, were employed to investigate the bonding characteristics and electronic structure of Fe(0)–, Pd(0)–, and Pt(0)–phosphine complexes with CO₂. The Fe(0) complexes exhibited the strongest CO₂ activation, characterized by substantial C=O bond elongation, significant charge transfer, and strong

π

-backdonation. In contrast, Pd(0) complexes showed minimal CO₂ activation, while Pt(0) complexes displayed intermediate behavior. The electronic effects of phosphine ligands were also analyzed, revealing that electron-donating phosphines enhance CO₂ activation, whereas electron-withdrawing phosphines weaken metal–CO₂ interactions. These findings provide key insights into the design of transition-metal-based catalysts for CO₂ conversion and utilization. Full article

(This article belongs to the Section Theoretical and Computational Chemistry)

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21 pages, 1459 KB

Open AccessArticle

Salicylic Acid Derivatives as Antifungal Agents: Synthesis, In Vitro Evaluation, and Molecular Modeling

by Ana Júlia de Morais Santos Oliveira, Danielle da N. Alves, Marcelo Cavalcante Duarte, Ricardo Dias de Castro, Yunierkis Perez-Castillo and Damião Pergentino de Sousa

Chemistry 2025, 7(5), 151; https://doi.org/10.3390/chemistry7050151 - 17 Sep 2025

Abstract

A series of twenty-five salicylic acid derivatives was synthesized and structurally characterized by ¹H and ¹³C-APT NMR and IR spectroscopic techniques, and HRMS analysis. The derivatives were subjected to biological evaluation against species of the genus Candida (C. albicans ATCC [...] Read more.

A series of twenty-five salicylic acid derivatives was synthesized and structurally characterized by ¹H and ¹³C-APT NMR and IR spectroscopic techniques, and HRMS analysis. The derivatives were subjected to biological evaluation against species of the genus Candida (C. albicans ATCC 90028, C. albicans CBS 5602, C. tropicalis CBS 94, and C. krusei CBS 573). In assays were used the broth microdilution method to determine the minimum inhibitory concentration (MIC) and verify the probable mechanism of action for antifungal activity. In the antifungal evaluation, compounds N-isobutyl-2-hidroxybenzamide (14), N-cyclohexyl-2-hydroxybenzamide (15), N-benzyl-2-hydroxybenzamide (16), N-4-methylbenzyl-2-hydroxybenzamide (17), N-4-methoxybenzyl-2-hydroxybenzamide (18), N-2,4-dimethoxybenzyl-2-hydroxybenzamide (19), N-4-fluorbenzyl-2-hiydroxybenzamide (22), and N-4-chlorobenzyl-2-hydroxybenzamide (23) were bioactive against at least one fungal strain. The compound with the best antifungal profile was N-cyclohexyl-2-hydroxybenzamide (15), which presented a MIC of 570.05 μM against most of the strains tested. The tests using ergosterol and sorbitol demonstrated that the compound does not act by altering cell wall functions or the plasmatic membrane in Candida species. The in silico analysis of 15 for antifungal activity in various biological targets suggested a probable multitarget mechanism. Therefore, the synthesis of salicylic acid derivatives resulted in compounds with a good antifungal profile. Full article

(This article belongs to the Special Issue Advances in Rational Drug Design: From Target Identification to Drug Lead Compounds)

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11 pages, 8680 KB

Open AccessArticle

Electron-Phonon Interaction in Te-Doped (NH₄)₂SnCl₆: Dual-Parameter Optical Thermometry (100–400 K)

by Ting Geng, Yuhan Qin, Zhuo Chen, Yuhan Sun, Ao Zhang, Mengyuan Lu, Mengzhen Lu, Siying Zhou, Yongguang Li and Guanjun Xiao

Chemistry 2025, 7(5), 150; https://doi.org/10.3390/chemistry7050150 - 16 Sep 2025

Abstract

Lead-free perovskite variants have emerged as promising candidates due to their self-trapped exciton emission. However, in ASnX₃ systems, facile oxidation of Sn(II) to Sn(IV) yields A₂SnCl₆ vacancy-ordered derivatives. Paradoxically, despite possessing a direct bandgap, these variants exhibit diminished photoluminescence [...] Read more.

Lead-free perovskite variants have emerged as promising candidates due to their self-trapped exciton emission. However, in ASnX₃ systems, facile oxidation of Sn(II) to Sn(IV) yields A₂SnCl₆ vacancy-ordered derivatives. Paradoxically, despite possessing a direct bandgap, these variants exhibit diminished photoluminescence (PL). Doping engineering thus becomes essential for precise optical tailoring of A₂SnX₆ materials. Herein, through integrated first-principles calculations and spectroscopic analysis, we elucidate the luminescence mechanism in Te⁴⁺-doped (NH₄)₂SnCl₆ lead-free perovskites. Density functional theory, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) confirm Te⁴⁺ substitution at Sn sites via favorable chemical potentials. Spectral interrogations, including absorption and emission profiles, reveal that the intense emission originates from the triplet STE recombination (³P₁ → ¹S₀) of Te centers. Temperature-dependent PL spectra further demonstrate strong electron–phonon coupling that induces symmetry-breaking distortions to stabilize STEs. Complementary electronic band structure and molecular orbital calculations unveil the underlying photophysical pathway. Leveraging these distinct thermal responses of PL intensity and peak position, 0.5%Te:(NH₄)₂SnCl₆ emerges as a highly promising candidate for non-contact, dual-parameter optical thermometry over an ultra-broad range (100–400 K). This work provides fundamental insights into the exciton dynamics and thermal engineering of optical properties in this material system, establishing its significant potential for advanced temperature-sensing applications. Full article

(This article belongs to the Topic Materials, Structure Designs and Device Fabrications for Highly Efficient/Long Lifetime Organic Light-Emitting Diodes)

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13 pages, 893 KB

Open AccessArticle

Subcritical Extraction of Rosa alba L. in Static and Dynamic Modes

by Ana Dobreva, Daniela Nedeltcheva-Antonova, Kamelia Gechovska, Nenko Nenov and Liudmil Antonov

Chemistry 2025, 7(5), 149; https://doi.org/10.3390/chemistry7050149 - 15 Sep 2025

Abstract

The chemical composition of Rosa alba L. aromatic products extracted with liquified 1,1,1,2-tetrafluoroethane (freon R134a) has been evaluated in static and dynamic modes of extraction. The yield varies in the range 0.039–0.048% for the different variants. In order to reveal the chemical composition [...] Read more.

The chemical composition of Rosa alba L. aromatic products extracted with liquified 1,1,1,2-tetrafluoroethane (freon R134a) has been evaluated in static and dynamic modes of extraction. The yield varies in the range 0.039–0.048% for the different variants. In order to reveal the chemical composition and aroma profile of the extracts, they were analyzed by means of gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame ionization detection (GC-FID). As a result of the analysis, more than 80 compounds with concentrations higher than 0.01% were identified and quantified in the extracts, representing 92.7, 88.4, and 88.0% of the total content. The study indicated that 2-phenyl ethanol (12.57–14.97%), geraniol (12.09–14.82%), nerol (5.90–6.39%), benzyl alcohol (3.63–5.34%), and citronellol (3.21–4.04%) were the main components of the aroma-bearing fraction. The solid phase consists mainly of nonadecane+nonadecene (15.21–16.85%), heneicosane (11.81–13.78%), and tricosane (2.46–2.96%). In addition, olfactory evaluation of the extracts was performed. The comprehensive assessment of the quantitative and qualitative characteristics of the extracts indicates that the static, one-stage mode is the most appropriate for the subcritical extraction of R. alba blossoms with freon R134a. Full article

(This article belongs to the Section Biological and Natural Products)

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20 pages, 1539 KB

Open AccessReview

Isolation, Synthesis, and Use of Natural Photosensitizers in the Treatment of Central Nervous System Tumors

by Julia Inglot, Joanna Strzelczyk, Jadwiga Inglot, Dorota Bartusik-Aebisher and David Aebisher

Chemistry 2025, 7(5), 148; https://doi.org/10.3390/chemistry7050148 - 15 Sep 2025

Abstract

Cancer is one of the leading causes of illness and death in the world. It is observed that the main reason for the low effectiveness of cancer treatment is limited bioavailability. Another noted cause is the lack of specificity of conventional chemotherapeutics, which [...] Read more.

Cancer is one of the leading causes of illness and death in the world. It is observed that the main reason for the low effectiveness of cancer treatment is limited bioavailability. Another noted cause is the lack of specificity of conventional chemotherapeutics, which contributes to the destruction of not only cancer cells, but also normal cells, and consequently leads to serious adverse effects. In recent years, researchers have paid special attention to the use of photodynamic therapy. Another major step in this progress is turning to photosensitizing natural compounds, which we present in this review. Natural photosensitizers are being investigated for their potential to treat central nervous system (CNS) tumors using photodynamic therapy (PDT). These compounds, derived from natural sources, offer an alternative to synthetic photosensitizers, potentially minimizing toxicity and enhancing therapeutic efficacy. Research focuses on isolating, synthesizing, and evaluating these natural photosensitizers for their ability to selectively accumulate in tumor cells and be activated by light to produce cytotoxic reactive oxygen species, leading to tumor cell death. Full article

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13 pages, 1954 KB

Open AccessArticle

Temperature-Dependent Growth Mechanisms and Optical Properties of MgF₂ Thin Films Synthesized by Plasma-Enhanced Atomic Layer Deposition

by Shui-Yang Lien, Xiao Lin, Zhi-Xuan Zhang, Jing Zhang, Wen-Xuan Zhu, Chia-Hsun Hsu and Chen Wang

Chemistry 2025, 7(5), 147; https://doi.org/10.3390/chemistry7050147 - 15 Sep 2025

Abstract

MgF₂ films are prepared using plasma-enhanced atomic layer deposition (PEALD). The influence of substrate temperature on the growth behavior, chemical composition, and optical properties of MgF₂ films is systematically investigated. The experimental results show that the deposition process transitions through three [...] Read more.

MgF₂ films are prepared using plasma-enhanced atomic layer deposition (PEALD). The influence of substrate temperature on the growth behavior, chemical composition, and optical properties of MgF₂ films is systematically investigated. The experimental results show that the deposition process transitions through three distinct regimes: an incomplete-reaction regime at 100 °C, a self-limiting ALD window at 125–150 °C, and a chemical vapor deposition (CVD)-like regime above 175 °C. At 100 °C, incomplete surface chemistry yields low growth-per-cycle, carbon incorporation, and an elevated refractive index. Within 125–150 °C, films are near-stoichiometric, smooth, and exhibit a low refractive index ≈ 1.37 ± 0.003 at 550 nm. Above 175 °C, precursor decomposition drives non-self-limiting growth with increased roughness. As an application-level validation, a film grown at 125 °C used as a double-sided antireflection coating on glass increases transmittance from 92 ± 0.1% (bare) to 97.2% ± 0.2% at 550 nm. The average transmittance of 96.4 ± 0.2% over 380–780 nm can be achieved. Overall, this work establishes the relationship between deposition temperature and PEALD-MgF₂ film properties and demonstrates precise, low-temperature, non-corrosive deposition suitable for advanced optical antireflection coatings. Full article

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14 pages, 3604 KB

Open AccessArticle

Sustained Release of Antibacterial Therapeutic Elements from Functionalized Mesoporous Silica-Coated Silver Nanoparticles for Bone Tissue Engineering

by Lehao Han, Yuhan Zhang, Nian Liu, Jiajia Jing, Yanni Zhang and Qiang Chen

Chemistry 2025, 7(5), 146; https://doi.org/10.3390/chemistry7050146 - 10 Sep 2025

Abstract

Applying therapeutic elements to prevent injury from potential infections is a promising avenue in the development of novel bone substitutes; however, achieving controllable delivery of therapeutic ions is crucial to realizing their expected functions. In this study, a Ag nanoparticle core wrapped in [...] Read more.

Applying therapeutic elements to prevent injury from potential infections is a promising avenue in the development of novel bone substitutes; however, achieving controllable delivery of therapeutic ions is crucial to realizing their expected functions. In this study, a Ag nanoparticle core wrapped in an MSN shell was successfully synthesized using a one-pot sol–gel process. Subsequently, the produced Ag@MSN was functionalized with amino and carboxylic groups. The experimental results indicated that these core–shell-structured Ag@MSN spheres had a uniform size of ~60 nm and a specific area of 904.6 m²/g. Their release profiles, influenced by different surface charges, were investigated, with the aim of achieving sustainable release of Ag ions. The concentration-dependent biological effects of Ag@MSNs, including their anti-infection properties and biocompatibility, were comprehensively characterized in vitro, considering their potential for use as bioactive bone substitutes. Functionalized mesoporous silica nanoparticles significantly enhanced the sustained release profile of silver ions, achieving a cumulative release efficiency greater than 50% within 24 h. These nanoparticles also demonstrated exceptional antibacterial efficacy, with an inhibition rate surpassing 98% at a concentration of 30 μg/mL, while concurrently maintaining cell viability above 88%, indicating high biocompatibility. We achieved our goal of effectively decreasing the burst release of Ag to satisfy the intrinsic need for long-term resistance to bacteria in bone substitutes and stimulate osteoblast proliferation. Full article

(This article belongs to the Section Chemistry at the Nanoscale)

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19 pages, 2580 KB

Open AccessArticle

Manganese(I) and Rhenium(I) Chelate Complexes with 2-Azabutadienes (RS)₂C=C(H)-N=CPh₂: Topological AIM Bonding Analysis and Molecular Structure of fac-MnBr(CO)₃[(ⁱPrS)₂C=C(H)-N=CPh₂]

by Marek M. Kubicki, Abderrahim Khatyr and Michael Knorr

Chemistry 2025, 7(5), 145; https://doi.org/10.3390/chemistry7050145 - 9 Sep 2025

Abstract

The thioether-functionalized 2-azabutadiene (ⁱPrS)₂C=C(H)-N=CPh₂ L1 ligates to Mn(CO)₅Br to form the five-membered chelate compound fac-MnBr(CO)₃[(ⁱPrS)₂C=C(H)-N=CPh₂] MnPropBr, whose crystal structure has been determined from X-ray diffraction [...] Read more.

The thioether-functionalized 2-azabutadiene (ⁱPrS)₂C=C(H)-N=CPh₂ L1 ligates to Mn(CO)₅Br to form the five-membered chelate compound fac-MnBr(CO)₃[(ⁱPrS)₂C=C(H)-N=CPh₂] MnPropBr, whose crystal structure has been determined from X-ray diffraction data. In the crystal, different secondary intermolecular interactions, such as Br^…HC and π^…π, give rise to a supramolecular network. The electronic properties of the metal–ligand bonds in MnPropBr are similar to those of complex MnPhBr (with R = SPh instead of ⁱPrS); this also applies to a series of structurally analogous fac-ReX(CO)₃[(RS)₂C=C(H)-N=CPh₂] (X = Cl, Br and I; R = SⁱPr, SPh and S^tBu) rhenium complexes and are discussed on the basis of QT-AIM (Quantum Theory of Atoms in Molecules) calculations. New bond length/electron density relationships are proposed for the metal–halide bonds, including, for the first time, complexes of one given metal and all three corresponding halides. In order to obtain a set of coherent data, three manganese complexes that belong to the family fac-MnX(CO)₃[N∩N] (X = Cl, Br and I; N∩N is a chelating ligand with two coordinating N atoms) were included in this study. Full article

(This article belongs to the Section Physical Chemistry and Chemical Physics)

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15 pages, 2394 KB

Open AccessArticle

Nitrogen-Doped Biocarbon Derived from Alginate-Extraction Residues of Sargassum spp.: Towards Low-Cost Electrocatalysts for Alkaline ORR

by Aurora Caldera, Beatriz Escobar, Juan Briceño, José M. Baas-López, Romeli Barbosa and Jorge Uribe

Chemistry 2025, 7(5), 144; https://doi.org/10.3390/chemistry7050144 - 3 Sep 2025

Abstract

Extraction processes of alginates from Sargassum spp. generate a substantial number of solid residues that are commonly discarded. This study explores the sustainable transformation of these residues into nitrogen-doped biocarbon through chemical activation with KOH and nitrogen doping using urea. XRD, FTIR, SEM-EDX, [...] Read more.

Extraction processes of alginates from Sargassum spp. generate a substantial number of solid residues that are commonly discarded. This study explores the sustainable transformation of these residues into nitrogen-doped biocarbon through chemical activation with KOH and nitrogen doping using urea. XRD, FTIR, SEM-EDX, Raman spectroscopy, BET surface area analysis, XPS, and CHNS elemental analysis were used to characterize the materials. The doped and activated biocarbon (BDA) demonstrated excellent physicochemical properties, including a specific surface area of 1790 m² g⁻¹ and a mesoporous structure. Electrochemical evaluation in alkaline media revealed a current density of −4.37 mA cm⁻², an onset potential of 0.922 E vs. RHE, and a half-wave potential of 0.775 E vs. RHE. Koutecky–Levich analysis indicated a two-electron reduction pathway. The superior performance was attributed to the synergistic effects of high surface area, nitrogen functionalities (pyridinic-N and pyrrolic-N), and enhanced accessibility of active sites. These results highlight the potential of waste-derived, nitrogen-doped biocarbon as a sustainable and low-cost alternative for ORR electrocatalysis in alkaline fuel cells. Full article

(This article belongs to the Section Catalysis)

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11 pages, 639 KB

Open AccessArticle

Biocatalytic Reduction of α,β-Unsaturated Double Bonds of Curcuminoid Derivatives by Exserohilum rostratum

by Jânison Nazareno Pastana, Victória Lopes Ribeiro, Mayra Suelen da Silva Pinheiro, José Edson de Sousa Siqueira, Luana Cardoso Oliveira, Heriberto Rodrigues Bitencourt, Taícia Pacheco Fill, Andrey Moacir do Rosario Marinho and Patrícia Santana Barbosa Marinho

Chemistry 2025, 7(5), 143; https://doi.org/10.3390/chemistry7050143 - 3 Sep 2025

Abstract

Turmeric is a spice that has gained significant popularity in global cuisine. Beyond its culinary applications, it possesses significant medicinal properties, including antioxidant, anti-inflammatory, and antibacterial properties, which are attributed to its majority compound, curcumin. In this study, we synthesized three curcuminoid derivatives [...] Read more.

Turmeric is a spice that has gained significant popularity in global cuisine. Beyond its culinary applications, it possesses significant medicinal properties, including antioxidant, anti-inflammatory, and antibacterial properties, which are attributed to its majority compound, curcumin. In this study, we synthesized three curcuminoid derivatives via the Claisen–Schmidt method (1E,4E)-1-(2-methoxy-phenyl)-5-(3-methoxy-phenyl)-pent-1,4-dien-3-one (2a), (1E,4E)-1-(2-methoxy-phenyl)-5-(3,4,5-trimethoxy-phenyl)-pent-1,4-dien-3-one (2b), and (1E,4E)-5-phenyl-1-(2-methoxy-phenyl)-pent-1,4-dien-3-one (2c). The synthetic compounds were hydrogenated in the olefinic double bond (CH=CH) by biotransformation catalyzed by the fungus Exserohilum rostratum given (CH₂-CH₂) 3a, 3b, and 3c. All compounds were identified by NMR and MS. The compounds were evaluated for their antibacterial properties against Gram-positive and Gram-negative bacteria, with the results indicating good activity, highlighting that the bioreduction from 2a to 3a led to an improvement of up to eight times in the observed activity against S. typhimurium of 250 to 31.25 µg/mL. Additionally, compounds 2a, 2b, 3a, and 3b are not previously documented in the literature. Full article

(This article belongs to the Section Biological and Natural Products)

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11 pages, 1951 KB

Open AccessReview

Recent Advances in Materials for Uranium Extraction from Salt Lake Brine: A Review

by Panting Wang, Miao Lei, Junhang Huang, Yuanhao Li, Ye Li and Junpeng Guo

Chemistry 2025, 7(5), 142; https://doi.org/10.3390/chemistry7050142 - 3 Sep 2025

Abstract

With the rising importance of nuclear energy in the global energy landscape, the sustainable development of uranium resources has garnered increasing attention. Salt lake brine, as an unconventional uranium source, holds significant potential due to its relatively high uranium concentration and the co-occurrence [...] Read more.

With the rising importance of nuclear energy in the global energy landscape, the sustainable development of uranium resources has garnered increasing attention. Salt lake brine, as an unconventional uranium source, holds significant potential due to its relatively high uranium concentration and the co-occurrence of valuable elements such as lithium, boron, and potassium. However, the high salinity and complex ionic composition of brine environments pose considerable challenges for the efficient and selective extraction of uranium. In recent years, the rapid advancement of novel adsorbent materials has provided promising technological pathways for uranium extraction from salt lake brine. This review systematically summarizes recent progress in the application of inorganic and carbon-based materials, organic polymers with functional group modifications, and biomass-derived and green adsorbents in this field. The construction strategies, performance characteristics, and adsorption mechanisms of these materials are discussed in detail, with particular emphasis on their selectivity and stability under complex saline conditions. Furthermore, the application status and future prospects of emerging materials and techniques—such as photocatalysis and electrochemistry—are also explored. This review aims to offer theoretical insights and technical references to support the sustainable exploitation of uranium resources from salt lake brines. Full article

(This article belongs to the Section Green and Environmental Chemistry)

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18 pages, 556 KB

Open AccessReview

Pea-Derived Antioxidant Peptides: Applications, Bioactivities, and Mechanisms in Oxidative Stress Management

by Yiming Gan, Ni Xie and Deju Zhang

Chemistry 2025, 7(5), 141; https://doi.org/10.3390/chemistry7050141 - 2 Sep 2025

Abstract

Chronic injuries and diseases related to oxidative stress are major global concerns as they impose a great medical burden and lead to serious public health issues. Antioxidant peptides derived from pea protein can serve as potent antioxidants and food additives, contributing to address [...] Read more.

Chronic injuries and diseases related to oxidative stress are major global concerns as they impose a great medical burden and lead to serious public health issues. Antioxidant peptides derived from pea protein can serve as potent antioxidants and food additives, contributing to address the challenges posed by oxidative stress. This review will focus on the antioxidant effects of pea peptides demonstrated in various in vitro chemical, cellular, and in vivo antioxidant models. Additionally, this review also summarizes the regulatory role of pea peptides on the Nrf2 (NF-E2-related factor 2)/Kelch-like ECH-associated protein 1 (Keap1) pathway, aiming to elucidate their antioxidant mechanisms. Our review found that pea peptides with smaller molecular weights (<1 kDa) obtained through enzymatic hydrolysis or fermentation and/or those containing amino acids such as Glu, Asp, Gly, Pro, and Leu tend to exhibit higher antioxidant activity. These pea peptides exert their antioxidant effects by scavenging free radicals, chelating pro-oxidative transition metals, reducing hydrogen peroxide, inactivating reactive oxygen species, enhancing the expression of antioxidant enzymes, and reducing the accumulation of lipid peroxides. Our study provides a theoretical foundation for the development of pea resources and the processing of pea-related functional foods. Full article

(This article belongs to the Topic Natural Bioactive Compounds as a Promising Approach to Mitigating Oxidative Stress)

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