Scholarly Publications - Chemistry

Permanent URI for this collectionhttps://hdl.handle.net/11693/115489

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Open Access
Cooperative catalytic role of Co and Mn sites on LaCoxMn1−xO3 perovskite nanoparticles in CO and NO oxidation
(American Chemical Society, 2025-08-18) Ercan, Kerem Emre; Karatok, Mustafa; Say, Zafer; Kurt, Merve; Sika-Nartey, Abel Tetteh; Özensoy, Emrah
Perovskites have significant potential to improve efficiency, reduce the costs of conventional oxidation catalysts, and contribute to cleaner and more sustainable energy solutions. However, numerous structural factors influencing their catalytic performance are still a subject to debate. In this study, simple perovskite nanoparticles in the form of $LaCoO_3$ (LC) and $LaMnO_3$ (LM), as well as $LaCo_{x}Mn_{1–x}O_3$ (LCM)-mixed B-site perovskites with different B-site cations, were synthesized and their performances in $CO$ oxidation and $NO$ oxidation reactions were examined. The $LaCo_{0.8}Mn_{0.2}O_3$ catalyst exhibited the highest catalytic activity in both $CO$ and $NO$ oxidation reactions, surpassing the 1 wt $%Pt/γ-Al_2O_3$ benchmark nanoparticle catalyst and other currently investigated perovskite nanoparticles. Co sites (predominantly $Co^{3+}$) in the optimized $LaCo_{0.8}Mn_{0.2}O_3$ catalyst were found to be enriched in electron density, while Mn sites (mostly in $Mn^{4+}$ form) were found to be more electron deficient as opposed to LC and LM. $LaCo_{0.8}Mn_{0.2}O_3$ not only released significantly greater amounts of oxygen and generated larger extents of oxygen vacancies than LC and LM under reducing conditions but also achieved this at favorably lower temperatures. In light of the current results, we report that Co sites in LCM operate as the main active site during both $CO$ and $NO$ oxidation by enabling stabilization and activation of $O_2$ (ads), while Mn sites mainly serve as promoters by increasing the adsorption strength of $CO$ (ads) and $NO$ (ads) as well as facilitating oxygen vacancy formation and vacancy regeneration, where oxygen vacancies were also found to contribute particularly to the $NO$ oxidation reaction within the currently investigated thermal window. These findings demonstrate that the electronic properties of LCM can be systematically tailored at the nanometer scale in a versatile manner to address different reactivity requirements of challenging catalytic reactions.
Open Access
What more can be done with XPS? Highly informative but underused approaches to XPS data collection and analysis
(AVS Science and Technology Society, 2025-05-30) Baer, Donald R.; Camci, Merve Taner; Cant, David J. H.; Chambers, Scott A.; Cohen, Hagai; Aydogan Gokturk, Pinar; Morgan, David J.; Shchukarev, Andrey; Sherwood, Peter M. A.; Süzer, Şefik; Tougaard, Sven; Watts, John F.
Because of the importance of surfaces and interfaces in many scientific and technological areas, the use of x-ray photoelectron spectroscopy (XPS) has been growing exponentially. Although XPS is being used to obtain useful information about the surface composition of samples, much more information about materials and their properties can be extracted from XPS data than commonly obtained. This paper describes some of the areas where alternative analysis methods or experimental design can obtain information about the near-surface region of a sample, often information not available in other ways. Experienced XPS analysts are familiar with many of these methods, but they may not be known to new or casual XPS users, and sometimes, they have not been used because of an inappropriately assumed complexity. The information available includes optical, electronic, and electrical properties; nanostructure; expanded chemical information; and enhanced analysis of biological materials and solid/liquid interfaces. Many of these analyses can be conducted on standard laboratory XPS systems, with either no or relatively minor system alterations. Topics discussed include (1) considerations beyond the “traditional” uniform surface layer composition calculation, (2) using the Auger parameter to determine a sample property, (3) use of the D parameter to identify sp2 and sp3 carbon information, (4) information from the XPS valence band, (5) using cryocooling to expand range of samples that can be analyzed and minimize damage, and (6) using electrical potential effects on XPS signals to extract chemically resolved electrical measurements including band alignment and electrical property information.
Embargo
From salt-in-water to water-in-salt: How ion identity governs surfactant self-assembly in salt–water–nonionic surfactant mixtures
(American Chemical Society, 2026-09-29) Albayrak, Cemal; Li, Yizhen; Dağ, Ömer; Warr, Gregory G.
Self-assembled mesostructures derived from nonionic surfactants can be tuned by adjusting parameters, such as the hydrophilic–lipophilic balance or electrolyte content. Such tuning permits control of key functional properties including conductivity, mass transport, and rheology. Although salts have frequently been used to influence the phase behavior of nonionic surfactant mixtures, they are almost always treated as minor additives. In contrast, here we extended the salt concentration range to hydrous melt and even nearly anhydrous conditions in which the salt no longer acts as an additive but replaces water as the solvent component. To elucidate the effect of ion identity on phase behavior, partial pseudoternary phase diagrams of salt–water–C12E10 mixtures were constructed using NaNO3, Zn(NO3)2, Ca(NO3)2 and CaCl2. Each salt represents a distinct set of intermolecular interactions and gives rise to markedly different phase diagrams, demonstrating that salt selection, or using a mixture of salts, can be strategically employed to finely tune self-assembly across the full hydration window.
Open Access
A heterodox approach for designing iron photosensitizers: pentacyanoferrate(II) complexes with monodentate bipyridinium/pyrazinium-based acceptor ligands
(American Chemical Society, 2025-04-01) Schmidt, Heiner; Oglou, Ramadan Chalil; Tunçer, Hüseyin Orhun; Ulusoy Ghobadi, Türkan Gamze; Tekir, Şafak; Özvural Sertçelik, Kübra Nur; Ibrahim, Abdelrahman; Döhler, Lotta; Özçubukçu, Salih; Kupfer, Stephan; Dietzek-Ivanšić, Benjamin; Karadaş, Ferdi
The main obstacle in replacing well-established precious ruthenium photosensitizers with earth-abundant iron analogs is the short excited state lifetimes of metal-to-ligand charge transfer (MLCT) states due to relatively weak octahedral field splitting and relaxation via metal-centered (MC) states. In this study, we address the issue of short lifetime by using pentacyanoferrate(II) complexes and combat facile photodissociation by utilizing positively charged pyrazinium or bipyridinium ligands. We utilize femtosecond transient absorption spectroscopy alongside quantum chemical calculations to probe the excited states of three 4,4′-bipyridinium- or pyrazinium-based pentacyanoferrate(II) complexes. The 4,4′-bipyridinium-based complexes exhibit 3MLCT lifetimes of about 20 ps, while the pyrazinium-based complex exhibits a lifetime of 61 ps in an aqueous solution, setting a benchmark for cyanoferrate complexes. These results mark the foundation for a new group of easy-to-prepare iron photosensitizers that can be used for harvesting visible light.
Open Access
Nanoarchitectonic mesoporous Ni₁–ₓMnₓO electrodes: Charge capacity and oxygen evolution reaction electrocatalysis in alkaline media
(American Chemical Society, 2025-02-26) Amirzhanova Katırcı, Assel; Karakaya Durukan, Irmak; Dağ, Ömer
Stable electroactive mesoporous Ni₁–ₓMnₓO thin-film electrodes are fabricated over FTO and graphite rods using the molten-salt-assisted self-assembly (MASA) method. Ethanol solutions of two salts ([Mn(H₂O)₄](NO₃)₂ and [Ni(H₂O)₆](NO₃)₂ with varying Ni(II)/Mn(II) mole ratios, 1.0 to 0.1) and two surfactants (C₁₂H₂₅(OCH₂CH₂)₁₀OH, C₁₂E₁₀ and C₁₆H₃₃N(CH₃)₃Br, CTAB) are coated over a conducting substrate (FTO and graphite rod) to assemble the salt–surfactant lyotropic liquid crystalline (LLC) mesophase that is calcined to obtain a mesoporous Ni₁–ₓMnₓO thin-film electrode. Ni₁–ₓMnₓO is a solid solution up to x of 0.7, but it transforms the NiMnO₃, Mn₃O₄, and Mn₂O₃ phases in the samples with x values of 0.5 and higher at higher annealing temperatures. FTO and graphite-coated (F-Ni₁–ₓMnₓO and G-Ni₁–ₓMnₓO) electrodes have a high charge capacity, but the FTO-coated electrodes are unstable and undergo degradation. They display an increasing charge capacity during early CV cycles (or consecutive GCD measurements) but decay in capacity over long-term experiments. The G-Ni₁–ₓMnₓO electrodes are more robust and display high charge capacities (958 C/g in pure NiO and 720 C/g in Ni₀.₉Mn₀.₁O, close to the theoretical values). During the electrochemical tests, both pure NiO and Ni₁–ₓMnₓO electrodes transform to core-NiO/shell-Ni(OH)₂ and core-Ni₁–ₓMnₓO/shell-Ni(OH)₂ structures on the pore walls, respectively. The shell thickness decreases from 2.0 nm in pure NiO to 1.1 nm with 10% Mn(II) addition in Ni₀.₉Mn₀.₁O at 350 °C. Moreover, the shell thickness is also dependent on the pore-wall thickness that increases exponentially with annealing temperature (from 4.4 to 27.1 nm in pure NiO and 4.0 to 12 nm in Ni₀.₉Mn₀.₁O by increasing the temperature from 350 to 500 °C, respectively). It increases from 2.0 to 4.5 nm in pure NiO and 1.1 to 1.5 nm in the Ni₀.₉Mn₀.₁O electrodes at those temperatures, respectively, and determines the charge capacity of the electrodes. The addition of manganese significantly improves the stabilities of the electrodes but almost has no effect on the overpotential of the electrodes. Even though the charge capacity depends on the annealing temperature, OER performance almost shows no effect on the annealing temperature.
Open Access
Two-dimensional titanium disulfide nanosheets for enhanced capacity of zinc-ion capacitors
(John Wiley and Sons Inc, 2025-03-28) Baglicakoglu, Sumeyye Kandur; Oz, Sena; Ucar, Ali Deniz; Koçak, Yusuf; Durukan, Mete Batuhan; Özensoy, Emrah; Unalan, Husnu Emrah
Capacitors offer high power density, superior cycle stability, and fast charging, making them highly promising for energy storage. However, their energy density needs to be improved. Due to zinc’ s abundance, low cost, high capacity, and stability, aqueous zinc-ion capacitors (ZnCs) have garnered significant attention. ZnCs face challenges such as rapid capacity decrease and reduced lifespan due to strong electrostatic interactions, electrode material dissolution, and sluggish ionic diffusion. Bulk titanium disulfide (TiS2) has been investigated as an electrode material to overcome these disadvantages, but the effects of its two-dimensional (2D) structure have yet to be discovered. With this work, bulk TiS2 is exfoliated into semi-metallic 2D-TiS2 nanosheets using organolithium chemistry, optimizing it as a cathode material for ZnCs to enhance energy density. The 2D-TiS2 exhibited a specific capacitance of 214.3 F g−1 at 0.1 mV s−1 scan rate and a specific capacity of 116.4 mAh g−1 at a current density of 0.1 A g−1, while significantly outperforming bulk TiS2. This work highlights the potential of 2D-TiS2 to enhance the energy density of ZnCs through improved electrical conductivity and improved accessibility of ions through nanosheets, offering a new class of cathodes for enhanced energy storage.
Open Access
Time-resolved electrical potential pump – X-ray photoelectron spectroscopy probe developments for investigating dynamic processes occurring at electrochemical interfaces
(Elsevier B.V., 2025-12-15) Mahl, Johannes; Aydogan Gokturk, Pinar; Hamlyn, Rebecca; English, Damon; Süzer, Şefik; Qian, Jin; Crumlin, Ethan J.
Electrode–electrolyte interfaces are of critical importance in several fields, including renewable energy, corrosion, and environmental chemistry. However, investigating these interfaces under operational conditions poses considerable challenges due to the limitations of the instrumentation employed. While recent advancements in in situ and operando techniques have enhanced our comprehension of the steady-state properties of solid-liquid interfaces, the dynamic behaviors of these systems remain inadequately explored. This study introduces a time-resolved X-ray photoelectron spectroscopy (XPS) technique designed to capture transient reaction intermediates and charging dynamics at electrified interfaces. The presented proof-of-principle study demonstrates that electrochemical processes, represented by an equivalent electrical circuit (EEC) model, can be probed and understood using square wave voltage pulses of a potentiostat synchronized to the modified data acquisition of an XPS setup. This method offers a valuable alternative to traditional pump–probe techniques, facilitating the investigation of a broader range of electrochemical systems. A dedicated software package for analyzing time- and energy-resolved XPS with a focus on extracting parameters of the EEC is geared towards benchmarking different EECs in future real-world electrochemical experiments.
Embargo
Bright green and blue solid-state emitting carbon dots with optimized photoluminescence characteristics for fabrication of high-performance light emitting diodes
(Elsevier Ltd, 2025-06-06) Havasi, Nasrin; Sahraei, Reza; Soheyli, Ehsan; Lan, Yu; Lou, Qing; Houshmand, Fatemeh; Zheng, Guangsong; Phul, Ruby; Mutlugun, Evren; Shan, Chong-Xin
Luminescent carbon dots (CDs) possess a range of fundamental and technological advantages, including low-cost, and scalable preparation methods, high emission efficiency, tunable electronic properties, and adaptable surface characteristics. However, aggregation-caused quench in solid-state emission of CDs has constrained their applications in luminescent solar-concentrators, and light-emitting devices. This study introduces a rapid and straightforward microwave method for producing bright blue- and green-emissive CDs, with emission peaks at 440 nm and 520 nm, respectively. Blue-CDs showed excitation-dependent feature with a biexponential decay profile and average lifetime of 6.3 ns, while the green one signified an excitation-independent photoluminescence profile with longer average lifetime of 9 ns through biexponential fitting of decay plot. Upon optimization of experimental parameters, reproducible green emission with a high efficiency of 78 % was achieved in dimethyl sulfoxide (DMSO). The critical role of biurea as a nitrogen precursor was elucidated through experimental and computational investigations. Furthermore, owing to the bright solid-state emission of the synthesized CDs, they were utilized as color-converting layers in the fabrication of durable monochrome LEDs, yielding blue and yellowish-green emissions with Commission Internationale de L'Éclairage (CIE) coordinates of (0.16, 0.10) and (0.35, 0.57), respectively. This study highlights the potential of CDs for applications in light-emitting panels.
Embargo
Visible light-driven acetaldehyde production from CO₂ and H₂O via synergistic vacancies and atomically dispersed Cu sites
(John Wiley and Sons Inc, 2025-05-12) Lei, Jian; Wang, Zhongliao; Huo, Jinquan; Sang, Shuaikang; Zhang, Chao; Zhu, Enquan; Kong, Tingting; Karadaş, Ferdi; Low, Jingxiang; Xiong, Yujie
Acetaldehyde (CH$_3$CHO) is of great industrial importance and serves as a key intermediate in various organic transformations. Photocatalytic production of acetaldehyde from CO2 represents a sustainable route compared to conventional oxidation processes. However, current photocatalytic systems often face challenges, including limited product selectivity and dependence on sacrificial reagents. Here, we present a Cd$_{0.6}$Zn$_{0.4}$S (CZS) photocatalyst co-modified with sulfur vacancies and atomically dispersed Cu (Cu/CZS−Vs) for the efficient conversion of CO₂ to acetaldehyde. Charge density analysis reveals that sulfur vacancies induce charge accumulation around the adjacent metal atoms, creating active sites that strongly anchor CO₂ and H$^+$, thereby promoting CO₂ conversion while suppressing the competing hydrogen evolution reaction. The atomically dispersed Cu sites facilitate the conversion of key intermediates (i.e., *CHO and *CO) to the crucial C₂ intermediate *OCCHO, which can subsequently be converted to acetaldehyde. As a result, this catalyst achieves an acetaldehyde yield of 121.5 μmol g$^{−1}$ h$^{−1}$ with a selectivity of ca. 80 % via photocatalytic CO₂ conversion in the absence of sacrificial agents, along with a quantum efficiency of ca. 0.53 % at 400 nm, underscoring its potential for practical CO₂ conversion applications. These results are expected to pave the way for future developments in green chemical processes.
Open Access
The utility and limitations of distribution of relaxation times (DRT) methods for impedance analysis
(IOP Publishing, 2025-07-23) Orazem, Mark E.; Ülgüt, Burak
Distribution of Relaxation Times (DRT) models are gaining popularity among researchers employing electrochemical impedance spectroscopy, especially by those studying fuel cells. The main reason for this popularity is that DRT is deemed non-parametric, has a perceived ability to resolve processes with similar timescales, and is considered to provide a model-free description of impedance data. In this manuscript, we show that DRT results are strongly dependent on a user selected parameter and, because the DRT method assumes a specific model, the time constants obtained do not necessarily correlate with those associated with physical systems.
Embargo
Effect of calcination temperature on CO₂ methanation performance of LaCoO₃ perovskite catalyst precursors
(American Chemical Society, 2025-08-12) Demiröz, Ezgi; Kurtoğlu-Öztulum, Samira F.; Ercan, Kerem Emre; Erdivan, Beyzanur; Güleryüz, Berfin; Koçak, Yusuf; Ünal, Uğur; Özensoy, Emrah; Uzun, Alper
A series of lanthanum cobaltites (LaCoO₃) calcined at different temperatures (600, 700, 800, and 900 °C) were investigated as catalyst precursors for the CO₂ methanation reaction. Characterization data revealed that samples prepared at low calcination temperatures (i.e., 600 °C) exhibited a slightly distorted rhombohedral crystal structure, higher BET surface area, enhanced reducibility, and lower oxygen vacancy concentration as compared with catalysts calcined at higher temperatures. After additional reductive treatment at 400 °C following the calcination, the trend in oxygen vacancy concentrations was reversed, although the bulk crystal structure remained unchanged. Results of CO₂-temperature-programmed desorption measurements indicated that the reduced samples, especially those calcined at low temperatures, exhibited better CO₂ adsorption affinity, which is crucial for CO₂ activation. The catalytic activity of the reduced samples was evaluated under both differential and high CO₂ conversion conditions. Arrhenius plots showed little variation in the apparent activation energy, confirming XPS results that differences in the catalytic performance were attributed to the number of active sites rather than significant changes in the nature of the active sites. After successful activation of LaCoO₃ prior to the reaction, the r-LaCoO₃-600 catalyst demonstrated superior activity, achieving 73% CO₂ conversion and 95% CH₄ selectivity at a space velocity of 12,000 mL CO₂ gcat⁻¹ h⁻¹, at 350 °C and 40 bar, using a CO₂:H₂ ratio of 1:4. Additionally, a 72 h stability test of the r-LaCoO₃-600 catalyst under the same conditions showed slight deactivation, limited with only approximately 10% decrease in CO₂ conversion while maintaining high CH₄ selectivity. The methane space-time yield of 5959 gCH₄ kgcat⁻¹ h⁻¹ offered by the r-LaCoO₃-600 catalyst surpasses those of most of the ABO₃-type perovskites. This high performance is linked to its higher surface area, increased oxygen vacancy concentration after H₂ reduction, and greater cobalt dispersion post reaction. In contrast, samples calcined at higher temperatures developed larger Co species after reaction, attributed to the lower oxygen vacancy concentration in the reduced catalyst.
Open Access
A theranostic endoperoxide agent with targeted singlet oxygen release and concomitant fluorescence signals
(Royal Society of Chemistry, 2026-02-25) Yan, S.; Si, Y.; Qian, X.; Sun, R.; Wang, W.; Liu, Z.; Wang, Y.; Wang, L.; Akkaya, Engin Umut
To circumvent the lingering limitations of photodynamic therapy, we developed a novel naphthalene-derived endoperoxide through structural optimization of 1,4-dimethylnaphthalene. Strategic introduction of an amide group at the 2-position enabled precise modulation of steric and electronic properties, resulting in prolonged 1O2 release half-life (t1/2 = 8.6 h) compared to simpler derivatives. This temporal control is likely to result in more 1O2 release in tumor tissues, significantly enhancing the therapeutic effect. Our studies reveal that thermal cycloreversion drives 1O2 generation from these compounds, achieving potent cytotoxicity in cancer cell cultures (IC50 = 11.6 µM). In vivo evaluation using a murine 4T1 breast cancer model demonstrated marked tumor suppression following intraperitoneal administration, with no observable systemic toxicity at the therapeutic doses. To enable real-time evaluation of therapeutic efficacy, we designed a modular system combining a naphthalimide fluorescent group with an H2O2-responsive phenylboronic ester. This construct capitalizes on the pathological overproduction of H2O2, a well-established biomarker of tumor progression. When exposed to elevated H2O2 levels in cancer cells, the phenylboronic ester undergoes specific cleavage to generate hydroxyl groups. This structural transformation triggers a blue-to-green fluorescence emission change, providing direct visual confirmation of therapeutic activation within the tumor microenvironment.
Embargo
Understanding excited states in magic series Au₈ₙ₊₄(SR)₄ₙ₊₈ nanoclusters: role of size, ligands, and theory level
(American Chemical Society, 2025-11-06) Acharya, Dinesh; Han, Baoliang; Liang, Hao; Gupta, Rakesh Kumar; Wang, Zhi; Alkan, Fahri; Gao, Zhi-Yong; Azam, Mohammad; Sun, Di
The excited-state properties of metal nanoclusters have attracted considerable attention for potential applications in optoelectronics and biomedicine. However, the theoretical exploration of these properties, particularly emission mechanisms, remains challenging due to the high computational cost of excited-state structure optimization. Herein, we investigate the geometric and electronic structural changes upon photoexcitation in the magic series gold nanocluster Au₈ₙ₊₄(SR)₄ₙ₊₈ (R = H or phenyl, n = 3–6) using time-dependent density functional theory (TDDFT) and its approximate variant, DFT plus tight binding (TD-DFT+TB). Our results demonstrate that approximate methods, which combine full DFT-ground-state descriptions with the tight-binding approximation in linear-response calculations, offer a cost-effective and reliable approach for predicting size and ligand effects on the excited-state properties of gold nanoclusters. Key parameters such as the Stokes shift, charge-transfer character, and energy gap between the first singlet (S₁) and triplet (T₁) states show strong dependence on cluster size and the nature of the ligand shell, and these trends are well captured by the approximate methods. These results emphasize their potential for the efficient design of gold nanoclusters with tailored optical functionalities.
Embargo
Hydrogen-bonding-assisted assembly of stable high-nuclearity copper(I)-alkyne nanoclusters for X-ray scintillation
(Wiley-VCH Verlag GmbH & Co. KGaA, 2025-08-25) Han, Bao-Liang; Alkan, Fahri; Yuan, Zhi-Rui; Mahato, Paritosh; Wang, Zhi; Tung, Chen-Ho; Sun, Di
The construction of high-nuclearity, atomically precise copper(I)-alkyne nanoclusters remains a formidable challenge due to their high reactivity and strong aggregation tendency. Here, we report a hydrogen-bonding-assisted assembly strategy that enables the ambient-condition synthesis of two robust copper(I)-alkyne nanoclusters. Single-crystal X-ray diffraction reveals the different core structures including [(C₂)₈@Cu₅₀] (Cu₅₀) and [(C₂)₁₀@Cu₅₆] (Cu₅₆). Both clusters feature distinctive metal shells stabilized by synergistic Cu─C/O coordination interactions and an extensive outer-layer hydrogen-bonding network between the hydroxyl groups of 2-methyl-3-butyn-2-ol and CF₃COO⁻ ligands, enhancing molecular rigidity and inoxidizability. Notably, Cu₅₀ displays strong yellow phosphorescence and prominent X-ray-excited luminescence (XEL). More signiﬁcantly, it represents the ﬁrst high-nuclearity copper nanocluster to be processed into a scintillator ﬁlm, which exhibits promising X-ray imaging performance. The present work not only establishes a generalizable hydrogen-bond-assisted assembly strategy for constructing stable, high-nuclearity copper(I)-alkyne nanoclusters, but also demonstrates their practical applicability in X-ray scintillation, providing new insights into the synthetic design and functional diversiﬁcation of nanocluster-based materials.
Open Access
Cu single atom stabilized au nanoclusters on TiO₂ for efficient hydrogen production
(Wiley, 2026-02-07) Zhang, Wen; Zhou, Yu; Sun, Xinhao; Chen, Shuo; Nie, Qinxue; Li, Yangyang; Huang, Weixin; Karaboğa, Seda; Özensoy, Emrah; Yin, Baoqi; Liu, Yuanxu
Metal nanoclusters (NCs) with atomically precise structures are widely used for light energy conversion in photocatalysis. However, the challenges in utilizing the photogenerated charges and light-induced photocatalyst instability often result in poor photocatalytic performance. Herein, we investigate tailoring of the local photocatalyst environment and promotion of the charge carrier transfer to increase the reactivity and stability of Auₙ/Cu–TiO₂ photocatalyst in photocatalytic hydrogen evolution from water under UVA illumination via in situ characterizations and theoretical calculations. The interfacial interaction between Au NCs and TiO₂ is regulated by precisely-anchored Cu single atoms (SAs) acting as electron acceptors, which can facilitate electron transfer from TiO₂ domains to Au NCs, thereby increasing the electron density of Au NCs, expedite electron capture, and enhance hydrogen production efficiency. As a result, Auₙ/Cu–TiO₂ exhibits 16.67 mmol·g⁻¹·h⁻¹ H₂ production rate, 22.7% apparent quantum yield, excellent photocatalytic stability, and recyclability under UVA light irradiation. This work offers novel insights into the rational design of semiconductor photocatalysts promoted with metal NCs and SAs, highlighting the cooperation effect in high photocatalytic performance.
Open Access
Modulation of delayed fluorescence pathways via rational molecular engineering
(Nature Publishing Group, 2025-03-26) Debnath, Sanchari; Ramkissoon, Pria; Salzner, Ulrike; Hall, Christopher R.; Panjwani, Naitik A.; Kim, Woojae; Smith, Trevor A.; Patil, Satish
One of the key challenges in developing efficient organic light-emitting diodes (OLEDs) is overcoming the loss channel of triplet excitons. A common approach to mitigate these losses to enhance the external quantum efficiency of OLEDs is employing emitter molecules optimized for thermally activated delayed fluorescence (TADF) or triplet-triplet annihilation (TTA). However, achieving both in the solid state from the same organic chromophore poses a formidable challenge due to energetic and structural requirements needing to be met simultaneously. Here, we demonstrate TADF and TTA in donor-acceptor phthalimide derivatives by employing triphenylamine (TPA) or phenyl carbazole (PhCz) as a donor. Thin films of the TPA-substituted phthalimides doped in the poly(methyl methacrylate) matrix exhibit TADF emission from the singlet charge-transfer (CT) state. On the contrary, PhCz-substituted emitters display dominant TTA-induced delayed fluorescence in the neat film due to long-range molecular ordering that facilitates efficient triplet diffusion. The present study provides insight into how dual TADF-TTA delayed fluorescence can be realized in thin films of molecular semiconductors via rational molecular design.
Embargo
Can interpretation of electrochemical impedance spectroscopy data be automated? Where do artificial intelligence algorithms stand?
(Elsevier Ltd., 2025-11-21) Orazem, Mark E.; Ulgut, Burak
While automation of data interpretation has been successful for optical spectroscopy and chromatography methods, automated interpretation of electrochemical impedance spectroscopy data is confounded by the nonuniqueness of models used to interpret the data in terms of physical quantities. Where automation has been successful, the data are compared with known libraries of high-quality, well-characterized, and specific datasets. In this manuscript, use of automation for data interpretation is reviewed, and guidelines are proposed for those seeking to develop artificial intelligence algorithms for analysis of impedance data.
Open Access
Three-particle breakup amplitudes from wave-packet solutions of time-dependent Faddeev equations
(American Physical Society, 2025-06-23) Kuruoğlu, Zeki Cemal
A time-dependent wave-packet method is devised to compute three-particle rearrangement and breakup amplitudes over a wide range of collision energies from a single wave-packet solution of the time-dependent Faddeev equations (TDFE). The TDFE is solved in momentum space for a given initial wave packet using finite-element-type discretizations of the Jacobi momenta in terms of local basis functions. Central difference formula for the time derivative is used for the time propagation step. Projection of the postcollision wave packet on the two-particle bound and continuum states yield state-to-state (sharp energy) rearrangement and breakup S matrices, respectively. The proposed method is tested on a three-body model that is often used as a benchmark to compare different computational approaches to three-particle problem. The wave-packet results for rearrangement are in good agreement with the reference results from a time-independent calculation. With the rather coarse discretization grid used in the present calculations, one is able to recover the general qualitative features of the breakup process, but quantitatively the state-to-state breakup results are not on par with the rearrangement results.
Open Access
Scalable solvent-mediated nanoarchitectonics of high-surface-area mesoporous Ni₂P₂O₇ for enhanced electrochemical performance in alkaline media
(American Chemical Society, 2025-12-26) Ceran, Gözde; Karakaya Durukan, Irmak; Ulu, Işıl; Dağ, Ömer
Sol–gel synthesis provides a versatile and scalable route for producing high-surface-area materials. Here, we develop a facile sol–gel strategy for mesoporous nickel pyrophosphate Ni₂P₂O₇ using H₄P₂O₇, nickel nitrate, and Pluronic P123 in butanol- and ethanol-based media. These mixtures form homogeneous sols that gelate and, after drying and calcination at 300 °C, yield powders with surface areas up to 410 m² g⁻¹. In contrast, methanol systems─and certain ethanol conditions─phase-separate into precipitate and supernatant layers. After calcination, the solution and precipitate fractions produce mesoporous Ni₂P₂O₇, while the supernatant fraction forms Ni₃(PO₄)₂ with different textural properties. The materials remain amorphous up to 600 °C and crystallize into α-Ni₂P₂O₇ at 700 °C. Thin-film electrodes were prepared by spin-coating on fluorine-doped tin oxide and dip-coating on graphite, followed by calcination. In 1 M KOH, Ni₂P₂O₇ converts into ultrafine Ni(OH)₂ nanoflakes, with the transformed graphite-supported electrodes showing high oxygen evolution reaction (OER) activity and stability. Moreover, Ni₂P₂O₇ is stable in alkaline media (pH ∼13) when the P₂O₇⁴⁻ concentration exceeds ∼0.27 M in the electrolyte. This work demonstrates a simple, tunable route to mesoporous Ni₂P₂O₇ and reveals its conversion into highly active OER electrocatalysts (381 mV at 100 mA cm–2, 45 mV dec–1).
Open Access
Hypoxia triggered singlet oxygen and nitrogen mustard release towards a synergistic therapeutic action
(Royal Society of Chemistry, 2025-04-28) Yuan, Qiao; Yun, Nie; Yu, Si; Xiao, Qian; Yingxu, Wu; Zhihao, Chen; Tingting, Zan; Bing, Liu; Akkaya, Engin Umut
We report an endoperoxide and nitrogen mustard conjugate (Pyd-endo) as a prodrug that can release cytotoxic singlet oxygen and aromatic nitrogen mustard under hypoxic conditions. Cell culture experiments demonstrated the hypoxia-responsiveness of the pro drug and its ability to kill and inhibit the migration and proliferation of various types of cancer cells. Studies using tumor-bearing mice and a liposomal formulation demonstrated its anticancer utility in vivo. Our design not only addresses the challenges of tumor hypoxia and limited light penetration issues of PDT but also presents the power of the combined cytotoxic action of singlet oxygen and a chemotherapy agent.