Materials Research Center

Selective activation of CH4 under mild conditions to produce liquid oxygenates is central to low-carbon chemical manufacturing. While O2 or H2O2 are commonly used oxidants, the direct oxidizing role of H2O itself remains poorly defined. Here, we use Au–TiO2 as a prototypical nanointerface to disentangle the effects of H2O versus O2 on photocatalytic CH4 oxidation. In-situ EPR spin-trapping, high-pressure DRIFTS, and DFT reveal two distinct pathways. With H2O as the sole oxidant, photogenerated holes oxidize H2O to •OH, which abstracts H from CH4 to form •CH3; subsequent surface reactions yield CH3OH and HCHO. Computations indicate that roughly one-third of the generated •OH participates effectively in the productive sequence. In contrast, when O2 is present, interfacial electrons preferentially reduce O2 to •OOH; coupling of •OOH with •CH3 forms CH3OOH intermediates that evolve to CH3OH/HCHO, but the elevated •OOH flux also accelerates deep oxidation to CO2 and suppresses H2 evolution. These mechanistic differences in radical identity, intermediate pools, and apparent barriers translate into divergent selectivity. Under optimized, O2-free conditions (1 wt % Au–TiO2, 80 °C, 20 bar CH4, UV–vis; H2O as oxidant/medium), liquid C1 oxygenates are obtained at 7.7 mmol g–1 h–1 with 100% selectivity. The study reveals that tuning the oxidant and the interfacial radical landscape at a nanoscale metal–oxide interface governs the precision activation of CH4 and provides mechanistic insight into H2O-driven, selective methane oxidation on Au–TiO2.

Synthetic polymers are widespread in modern life and pose growing environmental problems, especially in agriculture, where water management and soil health are crucial. Eco-friendly materials that balance performance and environmental safety are desperately needed as sustainable alternatives remain understudied. This study emphasizes the potential of lignin, a naturally occurring, abundant, and underutilized biopolymer, and its conversion into lignin-based hydrogels. Lignin hydrogels offer distinct benefits for agricultural applications due to their inherent antibacterial, biodegradable, and biocompatible properties. Their ability to swell improves soil water retention, promotes plant development in drought-prone areas, and permits regulated release of fertilizer. Lignin-based hydrogels can promote sustainable agricultural methods and lessen the dependency on synthetic polymers by customizing these characteristics. This study points to potential advances in green polymer technology by highlighting their capacity to bridge the gap between environmental stewardship and agricultural production.

The free energy of hydrogen adsorption (ΔGH) is a key descriptor for hydrogen evolution reaction (HER) kinetics in acids, although it is often limited in explaining facet- and strain-dependent catalytic activity. Here, we investigate the role of tensile strain on Pt(111) surfaces, focusing on the competitive adsorption between hydrogen and water. Combining computational and experimental studies, we demonstrate that tensile strain enhances hydrogen and water adsorption, resulting in the 1.3-fold enhancement in exchange current density compared to unstrained Pt(111). Our findings suggest that the ΔGH-based HER trends may not fully capture the influence of interfacial factors under structural deformation.

The development of underwater-based Internet of Things has drawn much attention to fluorescence sensors for crucial technological advancement. Therefore, the technologies for underwater mechanoluminescence (ML) sensing have created various applications for sensors and self-powered waterproof displays. However, developing single-molecule-based intrinsically adaptive materials capable of responding to multiple stimuli with high sensitivity remains a challenge. Herein, a flexible sensor based on the fluorescent ligand DHN was fabricated using a PVDF polymer matrix to form PVDH, enabling the exploration of external-stimuli-responsive fluorescence enhancement under mechanical strain and underwater pressure. For PVDH, the transition from crystalline to amorphous state by mechanical stimuli boosted its photoluminescence by ∼75%, and stretching (strain ∼16%) the sensor boosted its photoluminescence by ∼145%, which is due to the formation of molecular aggregates in the amorphous state. Additionally, the increase in ML correlated with an output voltage of ∼4 V of the fabricated device under mechanical stress. The in-depth density functional theory (DFT) calculations further support the experimental observation by studying the charge distribution and orbital overlapping in the DHN ligand. Furthermore, the film shows clear visualization when subject to underwater pressure and stable fluorescence upon exposure to different impurities. Therefore, this study reveals the use of fluorescence and mechanochromic properties of the ligand for designing advanced underwater sensors for visualization and communication.

Macro-monomer (macromer) containing eight epoxy groups (SU-8), which is known as a photoresist for photolithography, was synthesized and subsequently converted into a series of epoxy-methacrylate macromers via epoxy ring opening with 2-hydroxyethyl methacrylate (HEMA). The resulting macromers were employed in 3D printing resin formulations. The epoxy to methacrylate conversion was confirmed using proton nuclear magnetic resonance (1HNMR) spectroscopy, Fourier Transform Infrared (FTIR) Spectroscopy, and titration. The glass transition temperature (Tg) increased from −25.7 to 12.5 °C with increasing methacrylate content, as determined by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) demonstrated a decrease in thermal stability as the methacrylate functionality increased, with the fully methacrylated macromer (FA) losing up to 62% of its weight between 150 and 330 °C. For the study of the photocuring kinetics, ultraviolet (UV)-FTIR, along with the mechanical properties, demonstrated improved curing rate, higher volumetric shrinkage, and enhanced mechanical performance with increasing methacrylation, indicating optimized performance for vat photopolymerization-based 3D printing.

Compositionally complex oxides have garnered increasing interest for their enhanced phase stability and tunable functional properties, yet their development as bulk single crystal scintillators remains limited. Herein, we report the Czochralski growth and characterization of (Gd1/4Y1/4Tb1/4Lu1/4)3Al5O12:Ce (GYTLAG), a compositionally complex garnet incorporating four dodecahedrally coordinated principal rare earth elements. The garnet phase was confirmed by powder and single crystal X-ray diffraction, and macroscopic defects are described. X-ray absorption near-edge structure measurements confirm the 3+ oxidation state of all rare earths and support their occupation of the same crystallographic site; white line intensity variations correlate with the anticipated segregation behavior. Elemental segregation is quantified by SEM/EDS and ICP-OES, and a linear trend was established between the segregation coefficient and the difference between each rare earth’s ionic radius (r) and the average ionic radius (AIR) of the dodecahedral site. This trend offers a predictive framework for compositional control in future REAG crystals grown by the Czochralski method. Photoluminescence and radioluminescence measurements reveal both Ce3+ and Tb3+ emission. Scintillation pulses exhibit four-component decay with dominant ∼230 μs and ∼1.2 ms components, and the light yield is estimated to be up to 43,000 ph/MeV under 137Cs γ-ray excitation. GYTLAG also demonstrates a strong radioluminescence efficiency and 50% lower afterglow at 20 ms compared to a LuAG:Ce reference, underscoring its promise for scintillator applications.

The decoupled synthesis of Fe-NC single-site electrocatalysts mediated by Lewis-acids enables high active site density and utilization. However, current approaches often rely on small organic molecules and suffer from low synthesis yields due to the high Lewis acid-to-precursor ratios required to achieve highly porous carbons. Here, a porous organic polymer (POP) based on 2,4,6-Triaminopyrimidine is utilized as a carbon-nitrogen based scaffold for the synthesis of Fe-NC electrocatalysts. By tuning the amounts of MgCl2·6H2O used both as porogen and active site templating agent, we achieve synthetic yields exceeding 45%, a significant improvement compared to the 6% yield from the molecular analogue and the highest reported for Mg2+ templated systems. Subsequent low-temperature exchange with Fe leads to atomically dispersed FeNx, minimizing Fe aggregation. The resulting materials exhibit high specific surface areas (>1000 m2 g-1) with micro-, meso- and macropores, which promote mass transport and active site accessibility. Compared to Fe-NC synthesized via direct pyrolysis of Fe-coordinated POP, the decoupled method enables significantly higher catalytic activity in both alkaline and acidic media, and delivers 1 A cm⁻² at 0.687 ± 0.004 VRHE in an alkaline gas diffusion electrode, highlighting its potential for practical oxygen reduction devices.

Aluminum nitride is a promising passivation material for GaN-based micro-light-emitting diode (micro-LED) devices. However, depositing high-quality thin films at low temperatures without plasma remains challenging because conventional methods often compromise film quality or substrate integrity. In this study, we investigated the growth and properties of aluminum nitride films by low-temperature thermal atomic layer deposition (ALD) using tris(dimethylamino)aluminum (TDMAA) and ammonia (NH3) at 200–350 °C. Density functional theory (DFT) calculations indicate that the TDMAA dimer has a lower activation energy than the trimethylaluminum (TMA) monomer when reacting with NH3, which enables film deposition at lower temperatures. In situ quartz crystal microbalance (QCM) analysis suggests that film growth proceeds via ligand exchange reactions, with four to five dimethylamine molecules being released from the TDMAA dimer during the first half-reaction. Self-limiting conformal growth was achieved up to 300 °C, with a growth rate of 1.87 Å/cycle at this temperature. ALD-grown aluminum nitride films exhibited excellent interfacial coherence with GaN substrates even at deposition temperatures as low as 225 °C. Near the substrate, the stoichiometric composition of AlN was observed, while at the film surface, nitrogen atoms were gradually replaced by oxygen upon exposure to air. Higher deposition temperatures reduced the oxygen content due to improved film density and crystallinity. This low-temperature thermal ALD process enables the fabrication of stoichiometric AlN films with excellent conformality and interfacial coherence with the GaN substrate. These nanoscale films, specifically produced by purely thermal ALD processes at 200 to 300 °C, are promising for passivation layers in GaN-based micro-LED devices, thereby enhancing their efficiency.

This article provides teaching material on classical and quantum electromagnetic field theory for undergraduate and graduate chemistry students. It focuses on the concepts of spontaneous emission and the photon as explained by quantum electromagnetic field theory. In general chemistry classrooms, these concepts are introduced early on using the well-known Jablonski diagram. However, we argue that the current approach to teaching spontaneous emission and the photon in chemistry needs to be re-evaluated in light of insights from quantum electromagnetic field theory. This article presents a revised proposal for teaching these topics.