Caio Vinícius Caetano

Optimizing charge transfer at the solid‐liquid interface remains a central challenge for photocatalytic hydrogen evolution, particularly in polymeric semiconductors with limited electron‐donating ability. Here, we demonstrate that Mg ²⁺ incorporated into poly(heptazine imide) (PHI) acts as a catalytic promoter by synergistically coupling semiconductor charge transport with Pt co‐catalysts, thereby overcoming kinetically limited interfacial electron transfer. Using H ₂ evolution as a model reaction, Mg incorporation into Na‐PHI enhanced the hydrogen evolution rate by more than 2.5‐fold and introduced a linear dependence on Pt loading, an effect absent in pristine Na‐PHI. In situ XANES reveals reversible electronic modulation of Mg ²⁺ exclusively in the presence of Pt and water, confirming its direct participation in interfacial charge mediation. Complementary photophysical, (photo)electrochemical, and molecular dynamics simulations indicate that Mg ²⁺ polarizes water molecules through a dynamic Mg ²⁺ ‐OH ^δ– H ^δ+ ‐Pt interfacial motif, facilitating proton transfer toward Pt while stabilizing hydroxide species. Beyond the activity enhancement, Mg‐PHI exhibits improved structural stability by resisting framework protonation during recycling. Collectively, these findings establish Mg ²⁺ as a catalytic promoter and demonstrate that interfacial charge‐bridge effects can be rationally heterogenized, providing a general strategy for enhancing photocatalytic hydrogen evolution through targeted interface engineering.

Microneedle arrays (MNAs) is a rapidly emerging technology with broad biomedical applications in drug delivery and biosensing. With sub‐millimeter dimensions and periodicity, MNAs possess geometries nearly ideal for biomedical devices operating within the terahertz (THz) spectral window. Because chirality is crucial to the function of deposited drugs and surrounding tissues, realizing chiroptical resonances within MNAs could impart new capabilities to microneedle‐based technologies. However, methodologies for fabricating chiral MNAs are largely unknown and their importance remains largerly unrecognized. Here, we present a pathway to arrays of chiral microneedles (ARCHIMs) that exhibit strong and predictable chiroptical resonances in the THz range. These chiroplasmonic microneedles were prepared by glancing angle deposition of two sequential gold layers. ARCHIMs with thin, non‐centrosymmetric caps on each needle exhibit strong chiral plasmonic modes characterized by distinct THz circular dichroism (TCD) bands and polarization rotations as large as 5 degrees. To emulate chiral drugs and biologics, we coated the ARCHIMs with L ‐ and D ‐cystine crystals. We found that chiral phonons in the biocrystals resonate with chiral plasmons in the microneedles; their coupling induces handedness‐dependent shifts in the TCD spectra. This photonic effect was quantitatively described using a modified temporal coupled mode theory that incorporates polarization‐dependent resonator parameters. Our findings demonstrate that ARCHIMs provide an effective, tunable, and scalable platform for exploiting chiral light‐matter interactions, opening new opportunities in TCD sensing, chiral diagnostics, chiral phonon detection and THz photonics.

Carbon nitrides are among the most efficient and extensively studied transition‐metal‐free photocatalysts, yet their industrial application is limited by high charge recombination, poor charge transport, and insufficient absorption above 460 nm. This study investigates how fine‐tuning the crystal structure of carbon nitrides helps to overcome these challenges and to enhance their photocatalytic performance. We used poly(heptazine imides) (PHIs) with various cations (M = H⁺, Na⁺, K⁺, Mg ² ⁺) as a model system. Na‐PHI exhibits the highest activity among PHIs with monovalent cations, as the combination of solvated Na⁺ cations and rotational defects, experimentally observed in this study for the first time, optimizes interlayer charge transfer. Greater photocatalytic efficiency observed for Mg‐PHI is attributed to the preservation of rotational defects and the higher oxidation state of Mg ² ⁺, which enhances charge density and facilitates charge transfer. Density functional theory (DFT) and spectroscopic analyses reveal that Na‐PHI and Mg‐PHI share a valence band dominated by nitrogens and a conduction band primarily influenced by carbons, with both cations contributing to n‐type doping. Mg‐PHI features sub‐gap impurity states, reducing the band gap and extending light absorption. Excited‐state molecular dynamic simulations further demonstrate that water molecules contribute more significantly to charge transfer. highlighting an additional key factor in optimizing photocatalytic performance.

This work presents a theoretical study of the interaction between carbon nanotubes (CNT), boron nitride nanotubes and gallium nitride nanotubes with pollutant diamines cadaverine and putrescine using density functional theory (DFT) implemented using SIESTA.

In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialized cities, such as NH₃, NO₂ and SO₂ in different configurations was studied. For this study, the single-walled (10,0) GaNNT was used. The analysis was done via the density functional theory implemented in the SIESTA simulation software. The analysis of the results shows that the air pollutants alter the properties of nanotubes when they interact with them. The stability analysis shows that the most stable configurations are those in which adsorption occurs through a chemical process. The systems remain semiconductors, but in the case of NO₂ and SO₂ molecules interacting with GaNNT, there was a significant reduction in the energy gap. Our results also indicate that GaNNT is a promising material to detect and remove NH₃ and NO₂ molecules from the environment; however, it may be not applicable to detect or remove SO₂, because the latter interacts strongly with the nanotube, which prevents the GaNNT from being reused.

Density functional theory based calculations were performed to study the modification of the electronic and structural properties originating from the interaction between the (10,0) GaPNT and the FeCl₃ and CrO₃ compounds, using the software SIESTA. The results show that, for both compounds interacting with the GaPNT, the structures remained practically the same with a small deformation. In all studied systems, FeCl₃ acts as an acceptor of electrons while CrO₃ as an electron donor. The binding energy showed that both the FeCl₃ and CrO₃ compounds interact strongly with the GaPNT through a chemisorption process. Projected density of states analysis shows that the electronic properties were drastically modified with the adsorption of the FeCl₃ compound on the GaPNT due to the appearance of localized states in the gap region. In all systems, the band gap was reduced except in the case of CrO₃ adsorbed outside the GaPNT, in which the band gap was increased. In the case of FeCl₃ adsorbed inside the GaPNT, the system became metallic, while all the other systems remained semiconductors.

In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialized cities, such as NH3, NO2 and SO2 in different configurations was studied. For this study, the single-walled (10,0) GaNNT was used. The analysis was done via the density functional theory implemented in the SIESTA simulation software. The analysis of the results shows that the air pollutants alter the properties of nanotubes when they interact with them. The stability analysis shows that the most stable configurations are those in which adsorption occurs through a chemical process. The systems remain semiconductors, but in the case of NO2 and SO2 molecules interacting with GaNNT, there was a significant reduction in the energy gap. Our results also indicate that GaNNT is a promising material to detect and remove NH3 and NO2 molecules from the environment, however it may be not applicable to detect or remove SO2, because the latter interacts strongly with the nanotube, which prevents the GaNNT from being reused.