Piotr Radomski

Two-dimensional transition and post-transition metal dichalcogenides (TMDs and PTMDs) are promising materials for applications in roomtemperature, physisorption-based gas sensing and monitoring. In recent years, the mechanisms behind the adsorption of electron-accepting molecules have been well established, leading to the development of composition-engineering pathways that may be used to enhance the chemiresistive signal, as well as to design and fine-tune selective devices. However, similar trends have yet to be found for the electron-donating species. Consequently, the present study employs density functional theory (DFT) methods to systematically compare the adsorption of three electron donors, hydrogen sulfide (H ₂ S), ammonia (NH ₃ ), and aniline (C ₆ H ₅ NH ₂ ), and one baseline acceptor, nitrogen dioxide (NO ₂ ), on semiconducting 1H-MoS ₂ , 1T-SnS ₂ , and 1T-ZrS ₂ monolayers. The set was selected to provide direct comparison of different substrate symmetries, d-block versus p-block metal centers, and example acceptor-versus donor-molecule behavior under identical theoretical description. It was found that donor analytes can experience substrate-dependent enhancement in charge transfer only when their HOMO lies sufficiently high in energy. Accordingly, at the vdw-DF-cx level of theory, only aniline shows pronounced differences in adsorption, donating on average −0.049, −0.119, and −0.143 e to MoS ₂ , SnS ₂ , and ZrS ₂ , respectively, whereas NH ₃ and H ₂ S exhibit no comparable trend. This particular substrate order was correlated with the favorable positions of the conduction band edges as well as the spatial availability of the low-lying acceptor states. These results provide a theoretical basis for the mechanisms governing adsorption of donating species on pristine TMDs and PTDMs, and may aid in selecting a suitable material for physisorption-based devices.

This work is dedicated to investigating the spatially-resolved Raman and optical properties of Eu3+-doped Gd1-xLuxAlO3 (x = 0.0, 0.4, 1.0) single-crystalline mixed perovskite compounds prepared using the liquid phase epitaxy method. The films were grown onto YAlO3 single crystal substrates in a quasi-homoepitaxial mode. Particular attention is given to the Gd1-xLuxAlO3 mixed composition with lattice parameters close to YAlO3, ensuring the best film-substrate compatibility. Vibrational properties were studied using micrometer-step Raman probing across the samples’ cross-sections, revealing distinct features of the films, substrates, and the interface regions (transition layers). The observed Raman bands were assigned to characteristic ionic motions of AlO6 octahedra, and their frequency evolution with increasing Lu content was correlated with changes in A-site cation mass and pseudo-lattice parameter.Micro-luminescence spectroscopy was employed to evaluate the dopant 5D0 → FJ (J = 0–4) transitions as a function of cross-section depth and host composition. The results provide new insights into melt-material migration toward the substrate, a critical issue in flux-assisted growth. The characteristic 4f-4f bands of Eu3+ were analyzed and fitted using site-symmetry considerations and Judd–Ofelt theory, enabling clarification of the interplay between lattice structure, phonon dynamics, and activator-site symmetry in Gd1-xLuxAlO3 perovskites. These findings offer valuable guidance for the development of high-density, Eu3+-doped single-crystalline film scintillators for next-generation micro-imaging detectors.

Transition metal dichalcogenides (TMDs), including MoS ₂ , MoSe ₂ , MoTe ₂ , and WS ₂ , have emerged as a versatile class of two-dimensional (2D) materials for environmental applications, spanning pollutant capture, water purification, air remediation, chemical sensing, and catalytic conversion. Their high surface-to-volume ratios and tunable electronic properties enable their use as adsorbents for heavy metals and greenhouse gases, sensing platforms capable of ppb–ppt detection of toxic species such as NO ₂ , SO ₂ , and NH ₃ , and catalytic materials for green energy technologies, including the photocatalytic and electrocatalytic conversion of CO ₂ into value-added products. However, practical implementation remains limited by challenges in controlling sheet morphology and defect populations, which critically influence reactivity, selectivity, and long-term stability. Here, we present a bonding-centric perspective that links the environmental behavior of TMDs to the chemistry of the metal–chalcogen bond. We show that systematic variations in bond strength, polarity, and charge redistribution across the MoX ₂ (X = S, Se, Te) series govern interactions at environmental surfaces and interfaces, including pristine basal planes, defect-engineered systems, and intercalated multilayer structures. These differences dictate adsorption strength, charge transfer, and catalytic pathways for environmentally relevant species. By unifying these effects within a single mechanistic framework, this perspective establishes design principles for tailoring TMD-based materials with enhanced selectivity, stability, and efficiency. In doing so, it outlines a pathway toward next-generation environmental technologies for climate action and sustainable resource management.

We present the results of a study on Raman and high-resolution luminescence spectroscopy of Ce ³⁺ -doped Tb ₃ Al ₅ O ₁₂ single crystalline films (SCFs) grown by the liquid phase epitaxy method onto Y ₃ Al ₅ O ₁₂ and Gd ₃ Al _2.5 Ga _2.5 O ₁₂ single crystal substrates.

Accurate treatment of van der Waals (vdW) interactions is essential for exploring the potential of transition metal dichalcogenides (TMDs) in sensing, energy storage, and catalysis. Here, we present a comprehensive benchmark of twelve representative 2H-phase TMDs: NbS2, MoS2, TaS2, WS2, NbSe2, MoSe2, TaSe2, WSe2, NbTe2, MoTe2, TaTe2, and WTe2, using a suite of density functional theory (DFT) approaches. These include the semi-local PBE functional (bare and with D2, D3, D3M, D3+BJD, and D3M+BJD corrections) and six non-local vdW density functionals (vdW-DF, vdW-DF2, vdW-DF-OB86, vdW-DF-OBK8, vdW-DF-CX, and vdW-DF2-B86R). The results reveal that while no single vdW scheme is universally superior, a consistent subset: PBE+D3, vdW-DF-CX, vdW-DF-OB86, and vdW-DF2-B86R, achieves a balanced and physically reliable description. Among these, vdW-DF-CX and vdW-DF2-B86R provide the most accurate and transferable performance, closely followed by the widely used PBE+D3, which remains a practical choice for adsorption and intercalation studies. In contrast, PBE+D2 shows erratic behavior for W- and Ta-based TMDs, while D3M-based corrections systematically overbind and original vdW-DF and vdW-DF2 underbind, leading to inaccurate layer separations. These results establish a clear hierarchy of vdW treatments for TMDs and provide concise, transferable guidelines for future first-principles studies of layered and hybrid materials where dispersive interactions are essential.

Intercalation within two-dimensional transition metal dichalcogenides (TMDs) presents an innovative frontier for catalysis, a strategy largely unexplored outside of energy storage applications. While these materials are promising, the fundamental impact of chalcogen identity (S, Se, Te) on interlayer chemistry is poorly understood, and systematic studies probing these effects are particularly rare. This leaves a critical gap in the rational design of 2D sensors and catalysts. This work addresses this gap through a first-principles investigation into the intercalation of CO and CO2 within pristine and vacant MoS2, MoSe2, and MoTe2 bilayers. While pristine materials exhibit weak interactions governed by the energetic cost of layer expansion, the introduction of a single chalcogen vacancy unlocks dramatically different and material-specific catalytic functions. These behaviors are dictated by an interplay between vacancy size, charge availability at exposed metal sites, and intermolecular interactions within the confined interlayer space. The compact S-vacancy in MoS2 is found to uniquely catalyze CO oxidation (2CO → CO2 + C) due to geometric constraints, while remaining inert to CO2. In stark contrast, the larger, more electron-rich vacancies in MoSe2 and MoTe2 are inactive for CO oxidation but instead promote the crucial CO2 reduction reaction (CO2 → CO + O). These findings establish that tuning chalcogen chemistry in concert with defect engineering provides a powerful and highly selective pathway for designing atomically precise catalysts for carbon oxide conversion.