Abstract: Integration of lead zirconate titanate (PZT) films on metallic substrates is important for flexible piezoelectric devices, but achieving highly textured crystallinity without detrimental interfacial diffusion or oxidation remains challenging. In this work, PZT thick films (~1.3 μm) were deposited on titanium substrates using radio-frequency magnetron sputtering at 400 °C followed by rapid thermal processing at 640 °C for 2.5 min. A conductive LaNiO₃ buffer layer was introduced to promote nucleation of the perovskite phase and suppress interfacial degradation. The resulting PZT films on LNO/Pt/Ti substrates exhibit a strong (001) preferred orientation and dense micro-structure. The films show a large remnant polarization Pr of ~61 μC cm^-2 and a low coercive field E_c of ~56 kV cm⁻¹ at 60 V, together with dielectric constants ε_r of ~1350–1612 and dielectric loss tanδ ≤ 0.06 in the frequency range of 1 kHz–1 MHz. Patterned Pt/PZT/LNO/Pt/Ti cantilevers yield a transverse piezoelectric coefficient e_31,f of ~ –6.7 C m^-2, significantly outperforming reported piezoelectric films deposited on Ti. These results demonstrate that controlled nucleation and rapid thermal crystallization enable highly textured PZT films on reactive metallic substrates, providing a viable route for flexible piezoelectric MEMS devices.

Abstract: Porous titanium materials exhibit tremendous potential in the field of photocatalytic dye degradation owing to their unique structural and performance advantages. Although traditional powder materials (such as TiO2 nanoparticles) possess high specific surface area and active sites, they suffer from issues of difficult recovery and low light utilization efficiency . Coating materials address the recovery problem by immobilizing the catalyst; however, their limitations including limited specific surface area, insufficient visible light response, and poor mechanical stability restrict their practical applications. In contrast, bulk materials with in-situ grown nano-sized titanium dioxide on the surface of a titanium core combine high specific surface area, enhanced visible light absorption capacity, and excellent mechanical stability, making them an ideal choice for photocatalytic dye degradation. In this study, nickel-doped porous titanium was used as the substrate, and Nix-TiO2 nanotube films with a three-dimensional (3D) network structure were successfully prepared via an in-situ hydrothermal method. The effects of nickel content (2.5 wt.%, 5 wt.%, 7.5 wt.%, 10 wt.%) and calcination temperature (350 ℃-750 ℃) on the structure, morphology, and photocatalytic performance of the composite materials were systematically investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption (BET) techniques were employed to characterize the phase composition, micromorphology, chemical state, and specific surface area of the samples. Methylene blue (MB, 20 mg/L) was selected as the target pollutant to evaluate the photocatalytic activity and stability of the catalysts under simulated sunlight. Results indicated that nickel did not enter the TiO2 lattice but formed nickel oxide (NiO), constructing a semiconductor composite structure. Among all samples, the Ni7.5-TiO2 catalyst exhibited the optimal photocatalytic performance, achieving a 98.35% MB degradation rate within 3 hours and maintaining excellent cyclic stability after 5 consecutive degradation cycles. The optimal calcination temperature was determined to be 450 ℃, at which TiO2 nanotubes were completely in the anatase phase with an intact 3D network structure and high crystallinity. Compared with pure titanium substrates, the porous titanium-based catalyst showed a significant enhancement in adsorption capacity, and nickel doping further improved this performance by increasing the specific surface area and providing more active sites. The synergistic effect of nickel doping and the porous titanium-based nanotube structure effectively narrowed the TiO2 band gap, inhibited the recombination of photogenerated carriers, and improved solar energy utilization efficiency. This study provides a feasible technical approach for the treatment of wastewater containing organic pollutants and enriches the research on modified TiO2 photocatalytic materials.

Abstract: Reactive oxygen species (ROS)-mediated cancer therapy has attracted extensive attention due to its high spatiotemporal selectivity and minimum side-effects. Herein, we report a nonanuclear Pd-based coordination cage of Pd6-TMPP(Ni), constructed from Ni-chelated TMPP(Ni) as the metalloligand and Pd2+ ions (H2TMPP = meso-tetrakis (6-methylpyridin-3-yl) porphyrin). Pd6-TMPP(Ni) integrates dual ROS-generation for cancer therapy, viz., hydroxyl radical (•OH) production and photoinduced singlet oxygen (1O2) generation. In vitro cytotoxicity assays against cancer cell lines NCI-H82 (lung cancer), A549 (lung cancer), KYSE-510 (esophageal cancer), and Te-1 (esophageal cancer), reveal its potent dark toxicity (IC₅₀: 1.867–2.107 μmol L−1) and phototoxicity (IC₅₀: 0.835–1.528 μmol L−1), which is attributed to enhanced intracellular ROS accumulation. This work develops a versatile therapeutic platform that harnesses Ni-induced •OH for chemodynamic therapy (CDT) and porphyrin-generated ¹O₂ for photodynamic therapy (PDT), thereby mitigating the oxygen dependence of conventional PDT.

Abstract: Previous work has attempted, often within the framework of strip yield-type models, to predict crack growth rates based on the accumulation of fatigue damage ahead of the crack tip as it moves through a structure. This study performs similar calculations using results from plastic 2D plane stress analyses run on a finite element (FE) model containing a sharp semi-circular notch representing an edge crack. Stress-distance profiles ahead of the crack tip (notch root) were extracted at the maximum and minimum points of a range of fatigue cycles with different loading amplitudes. These were used with data from smooth specimen Low Cycle Fatigue (LCF) tests to predict the build-up of fatigue damage at regularly spaced locations ahead of the crack tip and hence crack growth rates. The FE analyses were performed for a wide range of K_max values at loading R-ratios of 0, -1 and 0.5, and the growth rate predictions were compared with test data. The method was then extended to predict overload behaviour. The material studied was the nickel-based superalloy fine grain (FG) RR1000 at 20°C.

Abstract:

In this paper, the supersaturated solid solution of Al-Cu3-Si-Mg alloy prepared by molten metal die forging (MMDF) was used as the research object. The formation and evolution of precipitates during aging treatment were investigated through experiments at different temperatures and times, and the precipitation mechanisms and sequences of various precipitates were analyzed. The main precipitated phases formed in the supersaturated solid solution of Al-Cu3-Si-Mg alloy after aging treatment are θ(Al₂Cu), θ'(Al_3.6Cu₂), γ'(Al_0.63Mg_0.37) and η'(Cu, Si). Based on XRD and TEM analysis under different aging treatment conditions, the precipitation sequence is determined as follows: SSS → GP₀ → GP₀+γ'→GP₀+(γ'+γ)+θ''+η'→(γ'+γ)+(θ''+θ')+(η'+η)→(γ'+γ)+(θ+θ')+(η'+η)→(γ'+γ)+(θ+θ')+η→γ+θ+η. With increasing aging temperature and time, precipitates tend to accumulate at the α-Al grain boundaries. After aging treatment at 165-185 °C for 4 h, chain-like θ(Al₂Cu) precipitates are discontinuously distributed at the α-Al grain boundaries, disk‑shaped θ'(Al_3.6Cu₂) and θ''(Al₂Cu) phases mainly precipitate within the grains. When the temperature exceeds 185 °C, the chain-like θ(Al₂Cu) precipitates at the grain boundaries gradually become continuous, the amount of θ(Al₂Cu) phase in the grains increases significantly, θ''(Al₂Cu) disappears completely, and the size of θ'(Al_3.6Cu₂) decreases obviously. After aging treatment at 185 °C for 5-6 h, the chain-like θ(Al₂Cu) precipitates at the grain boundaries become more continuous, and their length fraction continues to increase with prolonged aging time.

Abstract: A binder-free Co₃O₄ nanoneedle electrode grown directly on nickel foam (Co₃O₄@NF) was fabricated by hydrothermal synthesis followed by calcination and evaluated for electrocatalytic nitrate reduction to ammonium. The integrated three-dimensional architecture combines the catalytic activity of Co₃O₄ with the high conductivity and open porosity of nickel foam, thus exposing abundant active sites, shortening electron-transfer pathways, and facilitating mass transport. Among the electrodes prepared at different calcination temperatures, Co₃O₄@NF calcined at 400 °C delivered the best performance. Under the optimal conditions of −1.4 V vs. Ag/AgCl, pH 7, and an initial NO₃⁻-N concentration of 50 mg L⁻¹, the electrode achieved 84.3% nitrate removal within 480 min together with 98.7% ammonium selectivity. Electrochemical measurements revealed a markedly enlarged electrochemically active surface area and reduced charge-transfer resistance after Co₃O₄ loading. Mechanistic analyses further suggested that nitrate reduction on Co₃O₄@NF proceeded predominantly through an indirect pathway while maintaining negligible nitrite accumulation. The electrode also showed good cycling stability and retained high ammonium selectivity in real water matrices. These results demonstrate that binder-free Co₃O₄ nanoneedles supported on nickel foam constitute a promising cathode architecture for coupling nitrate removal with ammonia recovery.

Abstract: Micro-nonuniformity, as a fundamental natural property, is widespread across a range of microscopic systems, such as polymer systems, biomacromolecular systems, and nanosystems; however, the construction of micro-nonuniform molecular systems has not yet been realized at the level of organic molecules with well-defined structural compositions. Inspired by the "chemical space" concept, I recently reported a study of the single-molecule mixture state; in this paper, I provide a detailed discussion of micro-nonuniformity and the concept of a "single-molecule mixture".

Abstract: This study investigates the effect of dust and environmental debris (soiling) on reflective components in Concentrated Solar Thermal (CST) systems, a phenomenon that significantly reduces specular reflectivity and overall optical efficiency. Recent research efforts in the field have focused on advanced coatings capable of modifying surface wettability to improve self-cleaning performance and reduce water consumption for maintenance. Traditional methods for evaluating wettability rely on static contact angle measurements to characterize hydrophobic or hydrophilic surfaces; however, this parameter alone does not adequately reflect actual water usage in cleaning operations, which is influenced by environmental conditions, particulate composition, and operational constraints.Experimental assessment in operational solar fields remains impractical, as no facilities are currently fully equipped with self-cleaning mirrors, leaving the real impact on water consumption largely unknown. To address this gap, a laboratory-based gravimetric methodology has been proposed to quantify water retained on mirror surfaces during cleaning. By systematically correlating surface wettability with water retention and cleaning efficiency under controlled conditions, this approach provides a predictive framework for estimating water use based on coating properties.The methodology offers a standardized way to compare self-cleaning surface technologies and supports the design of coatings that minimize water consumption while maintaining high reflectivity, ultimately contributing to more sustainable and efficient solar thermal systems.

Abstract: This study systematically investigated the preparation conditions of palygorskite/Fe₃O₄ composites. The grain size of Fe₃O₄ was analyzed by fitting the Williamson–Hall equation. Combined with the catalytic degradation experiments of methylene blue via the Fenton reaction, the influence of Fe₃O₄ grain size on the catalytic performance of the composite was elucidated. Under different preparation conditions, the Fe₃O₄ grain size in the composites exhibited distinct variation characteristics. With an increase in the Fe₃O₄ loading ratio, the Fe₃O₄ grain size gradually increased, accompanied by an enhancement in the catalytic degradation performance. When the preparation temperature was varied, the Fe₃O₄ grain size increased with rising temperature, whereas the catalytic degradation performance of the composite gradually declined. Increasing the mechanical stirring speed led to a decrease in the Fe₃O₄ grain size, and the catalytic degradation performance of the composite increased accordingly. The results indicate that the Fe3O4 loading amount, preparation temperature, and mechanical stirring intensity can all regulate the Fe3O4 grain size in the palygorskite/Fe₃O₄ composite. Moreover, loading an appropriate amount of Fe₃O₄ particles onto the palygorskite surface and reducing the Fe3O4 grain size can both effectively improve the catalytic degradation performance of the PAL/Fe₃O₄ composite.

Abstract: Ice accumulation on critical infrastructure surfaces threatens operational safety in aviation, power transmission, and transportation systems. Conventional anti-icing and deicing strategies, such as chemical deicers and energy-intensive active heating, have inherent drawbacks. These include environmental pollution, high energy consumption, and low efficiency. In recent years, photothermal-responsive superwetting surfaces have attracted widespread attention. They can harvest renewable solar energy and achieve efficient anti-icing and deicing through tailored interfacial wetting properties. This review summarizes photothermal superwetting surfaces based on the “water as a lubricating layer” strategy. This strategy reduces ice adhesion strength and enables low-energy deicing. It works by forming a continuous lubricating film via photothermally induced interfacial meltwater. We discuss photothermal conversion mechanisms and strategies to enhance performance for stable lubricating film formation. We also analyze the stagewise physics of anti-icing and deicing, focusing on the interfacial tribological behavior of the water film. Key engineering challenges are addressed, including mechanical durability and all-weather applicability. Finally, we clarify future research directions for industrial translation. This review aims to provide theoretical insights and technical pathways for developing next-generation anti-icing and deicing surfaces that are efficient, eco-friendly, and sustainable.

Abstract: Sodium alginate was extracted from beach-cast Sargassum spp. collected along the coast of Puerto Progreso, Yucatán, Mexico, using two established pretreatment routes based on formaldehyde and ethanol. The study was designed to determine how extraction methodology influences alginate molecular structure and, consequently, its rheological performance. The ethanol-based route provided the highest extraction yield (up to 19.87%), whereas the formaldehyde route afforded alginate with higher intrinsic viscosity and viscosity-average molecular weight. Structural characterization by ¹H NMR revealed clear differences in monomer composition and sequence distribution, with ethanol-extracted alginate showing higher guluronic acid content, lower M/G ratio, and greater abundance of G-rich blocks. These structural differences were directly reflected in the viscoelastic behavior of Ca²⁺-crosslinked hydrogels. Alginate obtained by the ethanol route produced stiffer gels with the highest storage modulus, consistent with enhanced ionic crosslinking promoted by G-block-rich sequences, although with limited macroscopic cohesion due to lower molecular weight. In contrast, alginate obtained by the formaldehyde route showed a more balanced mechanical response associated with improved chain connectivity and network integrity. FTIR analysis confirmed the preservation of the characteristic functional groups of alginates in all samples. Overall, the results demonstrate that beach-cast Sargassum from the Yucatán coast is a viable source of sodium alginate and that extraction route is a key parameter governing its microstructure and rheological performance. These findings provide a structure–property framework for the valorization of stranded Sargassum biomass as a source of functional polysaccharides.

Abstract: Herein, we investigated the binding properties of four natural compounds extracted from Mediterranean plants—distachyasin, CxB, CxC, and magnoflorine—toward the G-quadruplex (GQ) formed by the KRAS22-RT sequence, a modified KRAS-derived oligonucleotide commonly used as a model of the KRAS oncogene, which adopts a single, well-defined parallel intramolecular GQ structure. Circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies revealed that distachyasin, CxC, and mag-noflorine induced only a slight stabilization of the GQ. In contrast, CxB significantly increased the GQ melting temperature, indicating a markedly stronger stabilizing effect. Notably, the reduced stabilizing effect of its diastereomer CxC highlights how the spatial arrangement of substituents around the core structure can strongly influence the binding properties of ligands towards GQs. Finally, the compounds were evaluated in three breast cancer cell lines and showed antiproliferative effects, particularly in the drug-resistant model.

Abstract: This study investigates the microstructural evolution and mechanical behavior of a Ni-based superalloy subjected to combined heat treatment and laser processing. Special emphasis is placed on the quantitative analysis of γ′ Ni₃(Al,Ti) and η (Ni₃Ti) phase distributions using SEM-based statistical methods. OM/XRD were employed for initial structural and phase identification, followed by detailed microstructural characterization using SEM/EDS. The results reveal that γ′ precipitates exhibit a fine and uniform distribution with a high number density, whereas the η (Ni₃Ti) phase appears as relatively coarse and sparsely distributed particles. Statistical size distribution analysis demonstrates that processing parameters significantly influence precipitate morphology and phase stability. Laser treatment promotes redistribution of γ′ precipitates and suppresses η (Ni₃Ti) phase formation, resulting in improved microstructural homogeneity. Mechanical characterization shows a strong correlation between γ′ Ni₃(Al,Ti) phase refinement and enhanced hardness and tensile properties. Fractography analysis indicates predominantly ductile fracture behavior with microvoid coalescence. The findings provide a quantitative understanding of phase evolution and establish a microstructure property relationship for optimizing Ni-based superalloys through advanced processing techniques.

Abstract: This study investigates the energy-efficient mechanochemical activation of fly ash derived from Kazakh coals for the development of sustainable cementitious composites. The ap-proach aims to enhance the reactivity of aluminosilicate materials while reducing the en-ergy demand and carbon footprint associated with conventional clinker-based cement production. Mechanochemical activation was performed to increase the specific surface area and in-duce structural defects in the glassy phase of fly ash, thereby improving its reactivity. Chemical activation using sodium hydroxide (NaOH) was applied to promote intensive pozzolanic reactions and accelerate dissolution kinetics. The optimal activation conditions were identified as 15 min of mechanical treatment com-bined with 4% NaOH. Under these conditions, the compressive strength reached 35.5 MPa at 28 days, exceeding that of the reference cement (35.0 MPa). At fly ash contents of 15–20%, the composites maintained or improved strength, whereas an increase to 30% resulted in a reduction to 31.5 MPa. Mechanical activation increased the specific surface area to approximately 4800–5000 cm²/g; however, prolonged grinding (up to 30 min) led to particle agglomeration and a de-crease in strength to about 28 MPa. Chemical activation enhanced reaction kinetics without significantly affecting particle fineness. Microstructural analysis revealed the formation of a dense and homogeneous matrix dom-inated by C–S–H, C–A–S–H, and N–A–S–H gel phases with reduced porosity. The com-bined activation approach demonstrated a clear synergistic effect, enabling up to 20% ce-ment replacement without loss of performance. Importantly, the proposed method provides a low-energy pathway for the utilization of industrial waste, contributing to reduced clinker consumption and lower CO₂ emissions. The results highlight the significant potential of Kazakhstan’s industrial by-products for the production of energy-efficient, environmentally friendly, and cost-effective construction materials.

Abstract: Agrivoltaics (Agri-PV) represents a promising solution to improve land-use efficiency by simultaneously allowing crop growth and photovoltaic (PV) energy generation, with additional benefits for crop production if properly engineered. However, when crystalline silicon (c-Si) PV modules are used for Agri-PV, even in semi-transparent configurations, shading occurs over crops, potentially reducing agricultural yields. Enhancing light diffusion is a key strategy to partially compensate for this effect, as diffuse light is more efficiently utilized by most plants. This study aims at engineering the transparent section of a semi-transparent c-Si PV module, assessing its optical, light-scattering, and efficiency-related properties for Agri-PV applications. The experimental work involved fabricating and testing various transparent stack configurations and mini-module prototypes to evaluate their suitability for Agri-PV integration. Optical characterization using a spectrophotometer revealed that certain stack configurations significantly enhance light diffusion, while maintaining good transmittance values for crops growth. To further analyze angular light scattering, a custom-built setup to measure the Bidirectional Transmittance Distribution Function (BTDF) was developed. The results showed that primarily anti-glare films (AG) and secondarily specific encapsulants (TPO) and flexible layers can effectively improve light distribution, helping to mitigate shading effects. Following AG application, Haze values exceeded 89%, indicating enhanced light diffusion capabilities. The impact of different stacks on module efficiency was also assessed through mini-modules testing. Findings indicate that enhanced light diffusion can be achieved with minimal efficiency losses. Specifically, the application of the AG resulted in a reduction of the Cell-To-Module efficiency ratio (CTM_η) of less than 1%. These results confirm that semi-transparent PV modules can be optimized for Agri-PV applications without significantly compromising energy output.

Abstract: This study focuses on the investigation of the influence of chitosan (CS) and the nature of the support on performance of the hybrid catalysts (Pd-CS/support) in low-temperature hydrogenation of allyl alcohol (2-propen-1-ol). CS-containing palladium catalysts were prepared via sequential deposition of the polysaccharide and palladium onto metal oxide supports (commercial MgO, SiO₂, TiO₂ and synthesized alumina). The synthesized CS-modified palladium catalysts were compared with their polymer-free counterparts. The successful formation of catalysts was confirmed using TGA, XPS, HAADF-STEM, and viscosimetric analysis. The results of low-temperature hydrogenation of 2-propen-1-ol indicate that catalytic activity and selectivity are influenced by both the support nature and chitosan modification. Overall, the introduction of chitosan had a positive effect on both the structural (Pd nanoparticle dispersion and convergence of the electronic properties of the catalysts) and catalytic (activity and selectivity) properties. The obtained results may contribute to controlling reaction pathways in the desired direction in the selective valorization of platform molecules.

Abstract: This study examines the microspherical high-calcium fly ash (HCFA) and the high-strength binder material based on it by method of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS). The composition of 568 individual microspheres of the initial HCFA was determined and presented as ternary diagrams CaO–Al2O3–SiO2 and CaO–FeO–SiO2. The binder specimens have a compressive strength of 24–90 MPa at a curing time of 3–300 days. Their strength is close to that of CEM I 42.5N cement specimens with a curing time of up to 28 days, but exceeds it with a curing time of up to 300 days. The SEM-EDS method showed that the predominant composition of hydration products is concentrated in the high-calcium region of the CaO–Al2O3–SiO2 diagram with a CaO content of 60–80%. The SiO2 content in them is 15-30%, and their composition includes 1–15% Al2O3 and 5–14% FeO. The SEM-EDS method allowed us to understand the transformation of calcium silicate glass microspheres into C-S-H gel, which is the main component of the strengthening matrix. The results contribute to the data for development of models for predicting the effect of HCFA on the properties of composite binders.

Abstract: Candida albicans is an opportunistic fungal pathogen of clinical relevance, and plant-derived antifungal agents have attracted interest because of rising resistance to conventional drugs. This study evaluated the in vitro antifungal activity of Mespilodaphne quixos (Lam.) Rohwer essential oil (EO) against C. albicans, modelled its concentration-dependent response using a one-factor response surface methodology (RSM) design, and investigated the interactions of its constituents with selected fungal targets by molecular docking. Freshly collected leaves were subjected to steam distillation, and the EO was characterised by GC/MS. Antifungal activity was determined using the Kirby–Bauer disc diffusion method. A one-factor RSM design was applied to model inhibition halo diameter as a function of EO concentration. Besides, 22 identified compounds were docked against 14-α-demethylase, Δ(14)-sterol reductase, and exo-β-(1,3)-glucanase. The EO was mainly composed of (E)-cinnamaldehyde (47.2%), caryophyllene (10.8%), and α-humulene (5.37%). The EO reached an inhibitory capacity of 87.3% relative to ketoconazole. The quadratic model showed good predictive performance. Molecular docking revealed favourable affinities for several sesquiterpenes: α-copaene showed the best interaction profile against 14-α-demethylase and Δ(14)-sterol reductase, whereas α-guaiene and spathulenol performed best against exo-β-(1,3)-glucanase. These findings provide preliminary in vitro and in silico evidence supporting the antifungal activity of M. quixos EO.

Abstract: Metal–organic frameworks (MOFs) offer unique opportunities for drug delivery due to their high porosity and the possibility of hosting large drug molecules within well-defined pore systems. In this work, the zirconium-based MOF NU-1000 was investigated as a carrier for the antineoplastic drug mitoxantrone (MTX). NU-1000 particles were synthesized and characterized by PXRD, SEM, and DLS, confirming their crystallinity, morphology, and size distribution. MTX loading was achieved by aqueous incubation and quantified by UV–Vis spectroscopy and thermogravimetric analysis, yielding a high loading capacity of ~40-43 wt%, with most of the uptake occurring within the first three hours. Structural characterization demonstrated that the MOF preserves its crystallinity and morphology after drug incorporation, while DLS results suggest that MTX is mainly accommodated within the internal pore system. To improve stability under physiological conditions, the composite was coated with NH₂-PEG-NH₂, resulting in PEG@MTX@NU-1000 particles with enhanced stability in phosphate-buffered saline. Cytotoxicity assays in HeLa cells showed that the PEGylated carrier is largely biocompatible, while PEG@MTX@NU-1000 exhibits a significantly enhanced antiproliferative effect compared to free MTX at short incubation times. These results demonstrate that NU-1000 is a promising platform for MTX delivery, combining high loading capacity, structural stability after PEGylation, and improved short-term therapeutic performance.

Abstract: Optical spectroscopy provides several useful information about polymeric thin films by combining interferometric and optical absorption data contained in the UV-Vis-NIR spectra. In particular, the UV-Vis-NIR spectrum of a thin polymeric film contains information about the film thickness, structural disorder, bandgap energy, type of electron transition model (direct/indirect, allowed/forbidden), cut-on wavelength (i.e., the opaque/transparent switching wavelength), etc. Here, these properties have been determined for a model semi-crystalline polymer (polyethylene terephthalate, PET) in form of ultrathin film before and after a mild mechanical deformation treatment (manual stretching). It has been found that EU and Eg parameters are not strictly depending on mechanical deformation due to their main dependence on chemical composition/constitution of the polymer.