Search Results (66)

Efficient biomass harvesting remains one of the primary barriers to the commercial feasibility of large-scale microalgal production. This study investigates the effect of different culture media on the surface physicochemical properties of Tetradesmus sp., with emphasis on their role in natural aggregation. Cultures were grown for 30 days under controlled light and temperature conditions using Blue Green 11 (BG11), Tris–acetate–phosphate (TAP), and deionized water supplemented with Bayfolan^® fertilizer. Surface hydrophobicity was assessed through microbial adhesion to solvents (MATS) and contact angle analysis, electrokinetic properties were evaluated by zeta potential measurements, and cell surface chemistry was characterized by attenuated total reflectance (ATR) sampling methodology for Fourier Transform Infrared (FTIR) spectroscopy. Across all treatments, Tetradesmus sp. exhibited inherent hydrophobicity, but Bayfolan^® supplementation yielded the highest contact angle (49.0 ± 0.9°) and the least negative free energy of interaction (ΔGsws = −26.36 mJ·m⁻²), indicating a stronger tendency toward self-aggregation. Zeta potential values remained consistently negative (−10 to −14 mV), with no significant variation among media, suggesting that hydrophobic interactions rather than electrostatic forces govern aggregation. ATR-FTIR spectra confirmed the presence of lipids, proteins, and carbohydrates, with changes in peak intensities reflecting metabolic adjustments to media composition. These results demonstrate that low-cost Bayfolan^® supplementation enhances surface hydrophobicity and aggregation, providing a sustainable strategy to facilitate biomass recovery and reduce harvesting costs in microalgal biorefineries. Full article

This study aims to investigate the vibrational, structural, morphological, optical, and magnetic properties of Zn_1−xCo_xO with 0.00 ≤ x ≤ 0.05 prepared by the sol–gel method via an amorphous citrate precursor. FTIR spectroscopy was used to follow the thermal decomposition process of the ZnO precursor, identifying acetate zinc as the intermediate main component. XRD and FTIR-ATR techniques showed only the single wurtzite crystalline phase with the presence of oxygen deficiency and/or vacancies, and secondary phases were not detected. SEM micrographs showed agglomerated particles of irregular shape and size with a high distribution and evidenced particles of nanometric size with a morphology change for x = 0.05. We detected high–spin Co²⁺ ions located in the tetrahedral core and pseudo–octahedral surface sites, substituting Zn²⁺ ions. The energy band gap of the ZnO semiconductor decreased gradually when the Co doping concentration was increased. M vs. H for undoped ZnO nanoparticles exhibited a diamagnetic signal overlapped with a weak ferromagnetic signal at room temperature. Interestingly, temperature-dependent magnetization showed superparamagnetic behavior with a blocked state in the low temperature range. The Co–doped ZnO samples evidenced a weak ferromagnetic signal and a paramagnetic component, which increased with x. The saturation magnetization increased until x = 0.03 and then decreased for x = 0.05, while the coercive field gradually decreased. Full article

Improving the end-of-life performance of polylactic acid (PLA) for food packaging requires strategies that enhance biodegradability, solubility, and dispersibility without compromising essential material properties. PLA-based films were produced by melt extrusion using polyvinylpyrrolidone (PVP) as a hydrophilic modifier, aiming to enhance the water uptake and affinity of PLA, which may potentially lead to faster environmental degradation. Two PVPs with distinct molar masses at varying concentrations were used to investigate their effects on the structural, thermal, mechanical, optical, and barrier behavior of the films. Thermal analysis revealed a slight depression in glass transition temperature, more evident in blends with low-molecular-weight PVP10, indicating increased chain mobility and partial miscibility. A two-step degradation process with extended thermal decomposition profiles was observed upon the inclusion of PVP. SEM and ATR-FTIR analyses confirmed enhanced dispersion and non-covalent interactions in PVP10-based blends, in contrast to the pronounced phase separation and micro-voids observed in PVP40-based systems. Mechanically, films containing 5 and 10 wt.% of PVP10 retained tensile strength and stiffness, whereas PVP40 led to embrittlement. Optical properties were modified by increasing the PVP content, resulting in greater opacity and color differences, which potentially offer benefits for light-sensitive packaging. Altogether, PLA films containing 5 and 10 wt.% of PVP10 demonstrated the most favorable balance between water affinity-oriented design and packaging-relevant performance. Full article

Numerous studies on specific cannabis compounds (cannabinoids and phenolic acids) have demonstrated their therapeutic potential, with their administration methods remaining a key research focus. Transdermal drug delivery (TDD) systems are gaining attention due to their advantages, such as painless administration, controlled release, direct absorption into the bloodstream, and its ability to bypass hepatic metabolism. The thin films obtained via pulsed laser deposition consist of micro- and nanoparticles capable of migrating through skin pores upon contact. This study investigates the interaction of phenolic compounds in hemp seeds with pulsed laser beams. The main goal is to achieve the ablation and deposition of these compounds as thin films suitable for TDD applications. The other key objective is optimizing laser energy to enhance the industrial feasibility of this method. Thin layers were deposited on glass and hemp fabric using dual pulsed laser (DPL) ablation on a compressed hemp seed target held in a stainless steel ring. The target was irradiated for 30 min with two synchronized pulsed laser beams, each with parameters of 30 mJ, 532 nm, pulse width of 10 ns, and a repetition rate of 10 Hz. Each beam had an angle of incidence with the target surface of 45°, and the angle between the two beams was also 45°. To improve laser absorption, two approaches were used: (1) HS-DPL/glass and HS-DPL/hemp fabric, in which a portion of the stainless steel ring was included in the irradiated area, and (2) HST-DPL/glass and HST-DPL/hemp fabric—hemp seeds were mixed with turmeric powder, which is known to improve laser interaction and biocompatibility. The FTIR and Micro-FTIR spectroscopy (ATR) performed on thin films compared to the target material confirmed the presence of hemp-derived phenolic compounds, including tetrahydrocannabinol (THC), cannabidiol (CBD), ferulic acid, and coumaric acid, along with other functional groups such as amides. The ATR spectra have been validated against Gaussian 6 numerical simulations. Scanning electron microscopy (SEM) and substance transfer tests revealed the microgranular structure of thin films. Through the analyzes carried out, the following were highlighted: spherical structures (0.3–2 μm) for HS-DPL/glass, HS-DPL/hemp fabric, HST-DPL/glass, and HST-DPL/hemp fabric; larger spherical structures (8–13 μm) for HS-DPL/glass and HST-DPL/glass; angular, amorphous-like structures (~3.5 μm) for HS-DPL/glass; and crystalline-like structures (0.6–1.3 μm) for HST-DPL/glass. Microparticle transfer from thin films on the hemp fabric to the filter paper at a human body temperature (37 °C) confirmed their suitability for TDD applications, aligning with the “whole plant medicine” or “entourage effect” concept. Granular, composite, thin films were successfully developed, capable of releasing microparticles upon contact with a surface whose temperature is 37 °C, specific to the human body. Each of the microparticles in the thin films obtained with the DPL technique contains phenolic compounds (cannabinoids and phenolic acids) comparable to those in hemp seeds, effectively acting as “microseeds.” The obtained films are viable for TDD applications, while the DPL technique ensures industrial scalability due to its low laser energy requirements. Full article

The aim of this study was to evaluate (a) the degree of conversion (DC%), (b) film thickness, and (c) the effect of film thickness on DC% in modern light-cured resin composite restoratives [Filtek Universal (F), Clearfil Majesty ES 2 Universal (M), Tetric EvoCeram (T) and Viscalor (V)] used for luting composite onlays before/after preheating. For (a), the luting composites placed at 150 μm film thickness under the onlays (4 mm thickness, 2.9% transmittance) were light-cured for 120 s (3 × 40 s top, buccal, lingual sites) before and after preheating (54 °C/5 min-F,M,T and 65 °C/30 s-V). The DC% was measured at central, middle and side locations along the median in-length axis by ATR-FTIR spectroscopy. Specimens polymerized without onlays (40 s, top) served as controls. For (b), film thickness was measured employing a modified ISO 4049 standard (37 °C plate temperature, 5 N load) before and after preheating, using a dual-cured resin luting agent as control. For (c), onlays were luted with preheated T at 150 and 350 μm film thickness and light-cured for 2 × (3 × 40) s and 3 × (3 × 40) s, employing directly irradiated specimens (60 s, 120 s) as controls. For (a), significant differences were found in F and T before and after preheating. Before preheating, significant differences were registered between F–T, F–M, F–V and V–T, whereas after they were registered between F–M, F–T and F–V. All these values were significantly lower than the controls. For (b), significantly lower film thickness was recorded after preheating (−16.1–−33.3%, highest in V), with a ranking of F, M > V > T (before) and F, M > T, V (after). All values were significantly higher than the control. For (c), increased exposure improved DC% in the greater spacer group, with the controls providing superior values. It can be concluded that the use of modern highly filled composites as luting agents for low translucency onlays may result in suboptimal polymerization and film thickness, warranting caution. Full article

Spent coffee grounds (SCGs), a by-product of coffee brewing, have high application potential. However, their high moisture content complicates conventional conversion without energy-intensive drying. This study explores a new route to convert SCGs to high-carbon bioproducts, such as hydrochar and bio-oil, through hydrothermal processing. The effect of the processing variables, i.e., temperature, residence time, and the application of the binary solvent as a reaction medium, on the distribution of the resultant bioproducts was investigated. The quality of the fabricated bioproducts was analyzed by means of instrumental techniques such as EA, ATR-FTIR, GC-MS, and GC-TCD-FID. Two dominant fractions were liquid bio-oil and solid hydrochar. The highest char yield (39 wt.%) was observed under milder conditions (low T and short residence times), while more severe conditions led to an increase in bio-oil formation, which reached a maximum of 46 wt.%. The resulting bio-oils were of similar quality, presenting high carbon content (71–74 wt.%) and energetic values (approximately 35 MJ/kg). Also, hydrochars showed a noticeable energy densification compared to raw materials, where the C content and HHV reached up to 73.8 wt.% and 30 MJ/kg, respectively. The addition of co-solvent to water improves the bio-oil yield as a result of the enhanced stabilization of reactive intermediates. Full article

The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes from aqueous solutions. As biomass, hazelnut shells are biodegradable and represent a sustainable alternative to synthetic adsorbents, thereby reducing the ecological footprint. Through a series of batch adsorption experiments, the influence of various parameters, including pH, contact time, concentration, and temperature, on adsorption capacity was examined. Characterization of the hazelnut shells was conducted using optical microscopy and ATR-FTIR, XRF, and XRD spectroscopy, confirming its suitability as a biosorbent. The analyzed isotherms showed that adsorption onto RHSs was best fitted by the Freundlich model, while adsorption onto MHSs was best fitted by the Temkin model. Kinetic studies demonstrated that the adsorption process is well described by the pseudo-second-order model, suggesting that chemical adsorption plays a significant role. The maximal adsorption capacity was 62.11 mg/g for RHSs and 80.65 mg/g for MHSs, highlighting the potential of hazelnut shells as an abundant, low-cost, and eco-friendly adsorbent. Furthermore, recycling studies indicated the feasibility of the adsorbent, underscoring its practical applicability in real scenarios. Full article

Background: Nabumetone (NAB) is a poorly soluble nonsteroidal anti-inflammatory prodrug (BCS class II drug) whose solubility is significantly improved by complexation with cyclodextrins (CDs). Methods: The solid complexes, in a 1:1 molar ratio, were prepared by mechanochemical activation by grinding, using β-cyclodextrin (β-CD) and its derivatives, hydroxypropyl- and sulfobutylether-β-cyclodextrin (HP-β-CD and SBE-β-CD). The complexation was confirmed by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR–FTIR). Obtained products were further characterized regarding their solubility, in vitro dissolution, permeability and chemical stability. Results: Co-grinding with HP-β-CD and SBE-β-CD yielded products that showed in vitro dissolution profiles in hydrochloric acid medium (pH 1.2) that were substantially different from that of pure NAB, yielding dissolution efficiency enhancements of 34.86 ± 1.64 and 58.30 ± 0.28 times, respectively, for the optimized products. Their in vitro dissolution and gastrointestinal permeability were also studied in a low-volume environment at pH 6.8, corresponding to the intestinal environment. Both β-CD derivatives increased NAB dissolution rate and NAB mass transport across the biomimetic membrane. The effect of β-CD derivatives on NAB chemical stability was studied under the stress conditions by the developed and validated UHPLC–DAD–HRMS method. In acidic conditions, pure and complexed NAB was prone to hydrolytic degradation, yielding one degradation product—pharmacologically inactive NAB metabolite. However, under the oxidative conditions at elevated temperatures, 10 NAB degradation products were identified from co-ground samples. All systems were stable during photo- and long-term stability studies. Conclusions: NAB complexes with HP-β-CD and SBE-β-CD are promising candidates for pharmaceutical product development. Full article

New asphalt mixtures have been improved by using fibers (polypropylene, polyester, asbestos, carbon, glass, nylon, lignin, coconut, sisal, recycled rubber, PET, wood, bamboo, and cellulose), reducing the temperature and compaction energy for their collocation, minimizing the impact on the environment, increasing the tenacity and resistance to cracking of hot mix asphalt (HMA), preventing asphalt drainage in a Stone Mastic Asphalt (SMA). Hence, this paper aims to evaluate the influence of the chemical (lignin content, ash, viscosity, degree of polymerization, and elemental analysis), morphological (SEM), spectroscopic (FTIR-ATR and XRD), and calorimetric (ATG and DSC) properties of celluloses from bagasse Agave tequilana Weber var. Azul (ABP), corrugated paperboard (CPB) and commercial cellulose fiber (CC) as Schellenberg drainage (D) inhibitors of the SMA. The ABP was obtained through a chemical process by alkaline cooking, while CPB by a mechanical refining process. The chemical, morphological, spectroscopic, and calorimetric properties were similar among the analyzed celluloses, but CPB and ABP cellulose are excellent alternatives to CC cellulose for inhibiting drainage. However, CPB is the most effective at low concentrations. This is attributed to its morphology, which includes roughness, waviness, filament length, orientation, and diameter, as well as its lignin content and crystallinity. Full article

UV-activated catalytic hydrosilation is a low-temperature crosslinking process that has attracted attention for its high efficiency and lower energy demand relative to thermal curing. In this study, formulations comprising industrially relevant model silanes and Pt photocatalysts trimethyl(methylcyclopentadienyl)platinum(IV) and trimethyl(pentamethylcyclopentadienyl)platinum(IV) (MeCpPtMe₃ and Cp*PtMe₃, respectively) were prepared with and without a photosensitizer (PS) and assessed for catalytic performance by a novel strategy. Photopolymerizations were initiated using different wavelengths from LEDs and monitored in real-time using an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) “well” strategy to track the degree of cure in ultra-thin films by consumption of hydride via the disappearance of the Si-H bending absorption band at 915 cm⁻¹. Irradiation of formulations with 365 nm excitation showed higher conversions relative to 400 nm light and improvements to calculated initial reaction rates by incorporation of a PS suggested increased sensitization to 365 nm irradiation. To the best of our knowledge, this is the first study to report catalytic performance, electronic absorption spectroscopic data, and the crystal structure of Cp*PtMe₃. Full article

A nature-inspired approach was employed through the development of dopamine-modified epoxy coating for anti-icing applications. The strong affinity of dopamine’s catechol groups for hydrogen bonding with water molecules at the ice/coating interface was utilized to induce an aqueous quasi-liquid layer (QLL) on the surface of the icephobic coatings, thereby reducing their ice adhesion strength. Epoxy resin modification was studied by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy (NMR). The surface and mechanical properties of the prepared coatings were studied by different characterization techniques. Low-temperature ATR-FTIR was employed to study the presence of QLL on the coating’s surface. Moreover, the freezing delay time and temperature of water droplets on the coatings were evaluated along with push-off and centrifuge ice adhesion strength to evaluate their icephobic properties. The surface of dopamine-modified epoxy coating presented enhanced hydrophilicity and QLL formation, addressed as the main reason for its remarkable icephobicity. The results demonstrated the potential of dopamine-modified epoxy resin as an effective binder for icephobic coatings, offering notable ice nucleation delay time (1316 s) and temperature (−19.7 °C), reduced ice adhesion strength (less than 40 kPa), and an ice adhesion reduction factor of 7.2 compared to the unmodified coating. Full article

Within the framework of plant biostimulation, a pivotal role is played by the achievement of low-cost, easily prepared nanoparticles for priming purposes. Therefore, in this report, two different synthetic strategies are described to engineer zinc oxide nanoparticles with an inulin coating. In both protocols, i.e., two-step and gel-like one-pot protocols, nanoparticles with a highly pure ZnO kernel are obtained when the reaction is carried out at T ≥ 40 °C, as ascertained by XRD and ATR/FTIR studies. However, a uniformly dispersed, highly homogeneous coating is achieved primarily when different temperatures, i.e., 60 °C and 40 °C, are employed in the two phases of the step-wise synthesis. In addition, a different binding mechanism, i.e., complexation, occurs in this case. When the gel-like process is employed, a high degree of coverage by the fructan is attained, leading to micrometric coated aggregates of nanometric particles, as revealed by SEM investigations. All NPs from the two-step synthesis feature electronic bandgaps in the 3.25–3.30 eV range in line with previous studies, whereas the extensive coating causes a remarkable 0.4 eV decrease in the bandgap. Overall, the global analysis of the investigations indicates that the samples synthesized at 60 °C and 40 °C are the best suited for biostimulation. Proof-of-principle assays upon Vicia faba seed priming with Zn5 and Zn5@inu indicated an effective growth stimulation of seedlings at doses of 100 mgKg⁻¹, with concomitant Zn accumulation in the leaves. Full article

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO₂, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm’s titration method, and pH_pzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (q_{m exp}) of MB and MG (349 mg g⁻¹ and 274 mg g⁻¹, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents. Full article

Porous starch can be applied as an adsorbent and encapsulant for bioactive substances in the food and pharmaceutical industries. By using appropriate modification methods (chemical, physical, enzymatic, or mixed), it is possible to create pores on the surface of the starch granules without disturbing their integrity. This paper aimed to analyze the possibility of obtaining a porous structure for native corn, potato, and pea starches using a combination of ultrasound, enzymatic digestion, and freeze-drying methods. The starch suspensions (30%, w/w) were treated with ultrasound (20 kHz, 30 min, 20 °C), then dried and hydrolyzed with amyloglucosidase (1000 U/g starch, 50 °C, 24 h, 2% starch suspension). After enzyme digestion, the granules were freeze-dried for 72 h. The structure of the native and modified starches were examined using VIS spectroscopy, SEM, ATR-FTIR, and LTNA (low-temperature nitrogen adsorption). Based on the electrophoretic mobility measurements of the starch granules using a laser Doppler velocimeter, zeta potentials were calculated to determine the surface charge level. Additionally, the selected properties such as the water and oil holding capacities, least gelling concentration (LGC), and paste clarity were determined. The results showed that the corn starch was the most susceptible to the combined modification methods and was therefore best suited for the production of porous starch. Full article

The constant change in microplastics (MP) due to exposure to environmental conditions leads to physical and chemical changes that enhance their ability to transport other pollutants, increasing the concern about their widespread presence in the environment. This work aimed to simulate the aging process of six MP (polyamide 6, unplasticized polyvinyl chloride, low-density polyethylene, polystyrene, polyethylene-co-vinyl acetate, polypropylene) in freshwater and seawater ecosystems at laboratory scale and evaluate its effects through optical microscope observation, Fourier transform infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR), Raman spectroscopy, and thermal gravimetric analysis (TGA). Through a combined experimental study of aged MP, the degradation by UV interaction was evidenced by the appearance of new infrared bands in the FTIR spectra assigned to ketones and hydroxyl groups. While Raman analysis and microscope images reveal the appearance of pores, wrinkles, and roughness in the MP surfaces. Variations in the temperature of the maximum weight loss of the MP were observed in the TGA analysis. The adsorption of chlorpyrifos (CPF), a common pesticide widely used in agriculture, by the pristine and aged MP was also studied. The highest affinity for CPF was observed for pristine LDPE and the lowest for PP. The batch adsorption studies revealed an increase in adsorption capacity as a consequence of the aging process for both MP. These results proved that the weathering effects caused changes in the behavior of MP, namely in the interaction with other pollutants. Full article