Globally, food production is increasing, leading to a concomitant rise in food waste (FW) generation, necessitating sustainable management strategies. This review critically examines various methods for converting FW into agricultural fertilizers, addressing the growing demand for sustainable nutrient management. FW, characterized by high moisture content and a diverse organic composition, presents both challenges and opportunities for fertilizer production. The review encompasses thermal methods (pyrolysis, gasification, hydrothermal carbonization, thermal hydrolysis), biological methods (composting, vermicomposting, anaerobic digestion), and innovative approaches such as hydrogel-based fertilizers. Furthermore, the review explores the risks associated with FW-derived fertilizers, focusing on potential contaminants such as microplastics, heavy metals, organic pollutants, and pathogenic microorganisms, alongside strategies for risk mitigation. The analysis highlights the potential of FW valorization to improve soil health, enhance crop yields, and reduce reliance on synthetic fertilizers, contributing to a circular economy. Future research directions are proposed, including optimization of existing technologies, long-term field studies, economic viability assessments, and the development of novel fertilizer formulations combining different processing methods. In conclusion, this review underscores the significant potential of FW as a resource for sustainable fertilizer production, emphasizing the need for continued innovation and rigorous evaluation to ensure its safe and effective application in agriculture.

We demonstrate a method for the realization of highly nonlinear optical 4-(4-dimethylaminostyryl)- 1-methylpyridinium tosylate (DAST) two-dimensional structures by a double-step technique. The desired polymeric structures were first fabricated by using the multiple exposure of the two-beam interference technique, and the DAST nanoscrystals were then prepared inside the air-voids of these photoresist templates, resulting in nonlinear periodic structures. The nonlinear properties were characterized by optical and scanning microscopies, as well as by second-harmonic generation technique. This nonlinear modulation is very promising for the enhancement of nonlinear conversion rates, such as terahertz generation, by using the quasi-phase matching technique.

Wound healing is a complex process that requires a comprehensive approach to treatment. Hydrogel materials modified with bioactive substances (BAS) are currently under active development. Such materials represent an alternative to conventional dressings. The inclusion of BAS in their composition opens the way to providing the required properties (antiseptic, antioxidant, etc.). Curcumin is one of a number of polyflavonoids that are being intensively studied for such use. Objective: in the current work, the method of obtaining gelatin-tannin hydrogels with BAS (curcumin), as well as the efficiency of isolation of the injected substance in vitro and the characteristics of its binding to the polymer matrix are considered. Materials and methods. The object of the study is gelatin-tannin hydrogels with curcumin. The structure of the materials was studied by IR spectroscopy, the sorption parameters were determined gravimetrically, the release of curcumin was studied by visible spectroscopy and analyzed using conventional pharmacokinetic models. Results. In the course of the work, hydrogel materials based on gelatin and tannin with a curcumin content from 0.1 to 1.0% were synthesized. It was found that the incorporation of curcumin into the polymer mesh was successful and curcumin is not released from hydrogels when swelling in distilled water. The introduction of curcumin into the formulation reduced the sorption capacity of hydrogels in distilled water from 15 g/g to 7-9 g/g. The Higuchi model (R2>0.95) was determined to be the most optimal model describing the process of curcumin extraction from materials. Using the description of the release kinetics, it was determined that the maximum release (22%) was achieved with a minimum curcumin content in the hydrogel (0.1 wt.%) and the minimum release speed. Conclusion. A method for the synthesis of gelatin-tannin hydrogels with curcumin has been developed. The structure of materials, sorption capacity, and the ability to release BAS have been studied. Further prospects for the inclusion of other BAS of a hydrophobic nature in the composition of hydrogels are shown.

Использование сгенерированных струй в качестве «микрорезцов» находит свое применение в лазерной хирургии. Такие способы лазерного воздействия используются для удаления новообразований, таких как межпозвоночные грыжи и кисты. К лазеру присоединяют оптоволокно, которое вводится к грыже или кисте через пункционную иглу. Для увеличения эффективности лазерного воздействия необходимо аккумулировать энергию на торце волновода при помощи нанесения поглощающего покрытия, которое должно обладать высокой адгезией к кварцу. В данной работе проведено исследование по разработке методики создания полимерных пленок золь-гель методом для использования в лазерной хирургии в качестве поглощающего покрытия. В роли прекурсора для формирования полисиликатной сетки, удерживающей малоразмерные частицы оксида кобальта, был выбран тетраэтоксисилан. В работе были исследованы оптические, морфологические и поглощающие свойства покрытий, полученные на кварцевых стеклах. Дополнительно растворы и полученные пленочные покрытия были изучены с помощью ИК-спектроскопии, результаты которой показали отсутствие качественного изменения золей при длительном хранении (до 3-х недель) и образование пространственной силикатной сетки и оксида кобальта в пленках. Исследование морфологии поверхности полученных покрытий показало, что для равномерного распределения синтезируемого оксида кобальта не нужны высокие концентрации солей кобальта. Поглощающие свойства образцов были протестированы с использованием ИК-лазера и тепловизора. Благодаря проведенным исследованиям выбран оптимальный состав покрытия для нанесения на кварцевые волноводы. The use of generated jets as «micro incisors» finds its application in laser surgery. Such methods of laser exposure are used to remove neoplasms, such as intervertebral hernias and cysts. An optical fiber is attached to the laser, which is inserted into the hernia or cyst through a puncture needle. To increase the efficiency of laser exposure, it is necessary to accumulate energy at the end of the waveguide by forming an absorbing coating, which should have high adhesion to quartz. In this work, a study was carried out on the development of a technique for polymer films by the sol-gel method for use in laser surgery as an absorbing coating. Tetraethoxysilane was chosen as a precursor for the formation of a polysilicate mesh holding small cobalt oxide particles. Optical, morphological, and absorbing properties of coatings obtained onto quartz glasses were studied in this work. Additionally, the solutions and the obtained coatings were studied using IR spectroscopy, the results of which showed the absence of a qualitative change in the sols during long-term storage (up to 3 weeks) and the formation of a three-dimensional silicate network and cobalt oxide in the films. The study of the surface morphology of the obtained coatings showed that high concentrations of cobalt salts are not required for the uniform distribution of the synthesized cobalt oxide. The absorbing properties of the samples were tested using an IR laser and a thermal imager. Owing to the research the optimal composition of the coating for the deposition on quartz waveguides was chosen.

Nowadays, plastic pollution attracts much attention both from society and scientists. The plastic pollution impact on the environment and human health requires assessment urgently, especially through experimental studies. However, such studies are still scarce because of the lack of standard methods for assessing their effects on living organisms. We have developed a process for manufacturing and staining PVC microparticles for using them in biological and ecological experiments. The electrospinning method has been used to manufacture PVC particles; their morphology and size have been analyzed. The obtained PVC particles are of narrow size range averaging 2–4 µm in diameter. They are successfully stained with the fluorescent dye Rhodamine B, which stands for the experiments performed in the seawater.

A method for creating of a three-dimensional nonlinear optical grating based on the alternation of layers with different nonlinear optical properties has been developed. The spatial structure of the lattice is formed by an active layer from a polymethylmethacrylate (PMMA) matrix with dimethyl amino -4-n-methylstilbazolium-tosylate (DAST) nanocrystals and a photopolymer used as an inactive layer. The absorption and refraction terahertz spectral dependencies of the photopolymerizable composition and the DAST - PMMA nanocomposite have been studied. Obtained results allow us to consider this material as a good candidate for terahertz photonics. The processes of terahertz generation in the DAST - PMMA nanocomposite by the optical rectification of femtosecond laser pulses have been investigated and high generation efficiency have been demonstrated. The nonlinear optical grating based on the indicated components was created and its structure was investigated.

A series of hybrid textures with variable topography and chemical composition were obtained on a hydrophilic steel (AISI 304) substrate with a hydrophobic MicroCoat (R) coating at the increasing incident nanosecond laser fluence from 1.4 J/cm(2) to 5.6 J/cm(2). The microtopography of the textured surface was studied by laser microscopy and scanning electron microscopy (SEM), while the chemical composition of the surface was determined by IR spectroscopy. The contact angles of water wetting in the textured areas varied versus laser fluence from about 100 degrees to 10 degrees, which was explained by both ablative removal of the hydrophobic polymer coating and the increase in roughness of the hydrophilic steel surface. The time dependence of the contact angle on the different textures, which demonstrated hydrophobization at different time scales depending on the texturing conditions, was analyzed. Autonomous directional flow was observed on laser-patterned wetting-gradient structures of various shapes, and the flow velocity of water droplets on these structures were measured. It was shown that the velocity of water drop spreading on the gradient structures depends on the difference in contact angles on adjacent spots. The various modules fabricated can be harnessed in chemical and biomedical microfluidic devices.

Topography-dependent tuning of water wettability was achieved on a stainless steel surface textured by nanosecond-laser pulses at different laser fluences, with the minimal contribution of the surface chemical modification. Such differently-wet neighboring surface spots were demonstrated to drive an autonomous directional water flow. A series of elementary microfluidic devices based on the spatial wetting gradients were designed and tested as building blocks of “green”, energy-saving autonomous microfluidic circuits.

An Erratum to this paper has been published: https://doi.org/10.1134/S0030400X21040287

Highly nonlinear optical 4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST) crystals have been successfully grown. The photobleaching effect was demonstrated by irradiation with an UV light at 405 nm during 120 h. The UV-Vis and terahertz absorption spectra of DAST in crystalline states before and after photobleaching were measured and compared. Results of photobleaching modification of DAST monocrystal have been demonstrated with the help of differential interference contrast microscopy (DIC). A possible explanation of photobleaching effect has been suggested. Since absorption in the terahertz range of crystalline materials is associated with vibrational modes of the crystal lattice, we can conclude that photobleaching leads to its destruction. Taking into account the obvious change of crystalline spectra in the UV-Vis and terahertz frequency range and the absence of changes in the molecular spectra from irradiated DAST in ethanol solution, we can conclude that the photobleaching process may be a photoactivated destruction of chemical in DAST molecules. The photobleaching technique was proposed to implement quasi-phase matching (QPM) structures for efficient nonlinear conversion by optical rectification.

Subject of Research. The paper presents research of photoactinic radiation effect on refractive indice of organic nonlinear optical co-crystals: 2.6-diaminopyridine-4-nitrophenol and 4-aminopyridine-4-nitrophenol. Method. The research technique included prolonged exposure of the organic nonlinear optical co-crystals of aminopyridine-nitrophenol to a light-emitting diode at a wavelength of 405 nm. In the exposure process of the studied co-crystals a sequential measurement of the refractive indices was carried out by Olympus STM6 instrumental microscope. Main Results. The increase in values of the refractive indices is observed for both co-crystals examined during the long photobleaching. We present circle diagrams for refractive indices of the organic aminopyridine-nitrophenol co-crystals under study. Practical Relevance. The results obtained show the possibility of creating structures based on organic co-crystals of aminopyridine-nitrophenol with a given distribution of refractive indices (periodic lattice and photonic crystal structure).

Edible films and coatings based on biopolymers to protect and extend the shelf life of food and medicine can be functionalized, by applying a holographic marker on the coating surface for marking products or sensing storage conditions. In this work, holographic markers were prepared on the surface of thin biopolymer coatings based on starch, gelatin, agar and also starch/gelatin and starch/agar blends by the nanoimprint method from a film-forming solution. The morphology of the surface of holographic markers using optical microscopy in reflection mode was examined, as well as the reasons for its formation using an analysis of the flow curves of film-forming solutions. It was found that the surface morphology of the marker strongly depends on the composition, consistency index of film-forming solution and miscibility of the components. It was shown that the starch/agar film-forming solution at the ratio of 70/30 wt.% has a low consistency index value of 21.38 Pa·s0.88, compared to 64.56 Pa·s0.67 for pure starch at a drying temperature of 30 °C, and the components are well compatible. Thus, an isotropic morphology of the holographic marker surface was formed and the value of diffraction efficiency of 3% was achieved, compared to 1.5% for the marker made of pure starch. Coatings without holographic markers were analyzed by tensile strength and water contact angle, and their properties are highly dependent on their composition.

Autonomous directional water flow was demonstrated on a laser-microstructured steel-supported polymethylmetacrylate (PMMA) film with a surface tension gradient. For this purpose, a 4 μm-thick PMMA layer on AISI 304 steel surface was raster-scanned in air in ablative mode by a 1064 nm, 100 ns laser beam in a number of lines, with the amount and topography of ablated PMMA analyzed by optical microscopy, profilometry and IR spectroscopy. Such scanning, performed at increasing incident fluences, produced a series of chemically and topographically modified, differently water-wet neighbouring mm-sized spots, autonomously driving single-droplet water flow along the surface tension (contact angle) gradient.

The influence of copper ion concentration on the absorption spectrum of Rhodamine B in molecular form in an alcohol solution and immobilized in a polymer hydrogel film was studied. The sensitivity of the system to the presence of copper ions at a concentration of 0.1 mg/l, sufficient for practical use, is shown. The insolubility of Rhodamine B in water when it is immobilized in the volume of a photopolymerizing hydrogel film makes it possible to create a chemosensor that is stable at long exposures and can sense ultra-small concentrations of the analyzed impurity.

The processes occurring during photobleaching of a new nonlinear optical co-crystal 2,6-diaminopyridine-4-nitrophenol-4 nitrophenolate are investigated. Using infrared spectroscopy of co-crystals, destruction of an aminopyridine-nitrophenol molecular complex by photoactinic radiation without breakage of aminopyridine and nitrophenol molecules integrity is shown. Differential scanning calorimetry and thermogravimetric analysis of the co-crystals showed a decrease in temperature of transitions of exposed co-crystals due to structural changes. Intensities of the second harmonic of the co-crystals under study were measured before and after photoactinic exposure; the results showed the decrease in the intensities of the second harmonic during prolonged illumination due to the structural changes in volume of the co-crystals confirming the breakage of the aminopyridine-nitrophenol molecular complex with preservance of the integrity of the molecules forming the molecular complex. Methods of terahertz absorption spectroscopy showed changes in absorption and a refractive index of a co-crystal in the range of 0.3-2.5 THz after the exposure to the photoactinic radiation, which can be interpreted as a result of destruction of the crystal structure. All the results obtained clearly showed that a co-crystal structure is disordered and the aminopyridine-nitrophenol bond is broken on the exposure to the photoactinic radiation, while the molecules of both components do not collapse, which leads mainly to disappearance of nonlinear optical properties. The investigated process is suitable for creating nonlinear optical lattices in the co-crystals using the photolithography method.

Methods for the preparation of DAST (4-N, N – dimethylamino–4'-N'-methyl stilbazolium tosylate) thin monocrystals with a thickness of a few micrometers, intended for electro-optics modulation were investigated. Thin-film single crystals are obtained, the shape and absorption spectrum of which confirms their crystalline structure of the “red” form DAST. Uniform color in the polarization contrast mode shows their monocrystallinity and uniform orientation. The materials are intended for intracavity modulation of laser radiation.

We studied the effect of the concentration of copper ions on the absorption spectrum of Rhodamine B in molecular form in an alcohol solution and immobilized in a polymer hydrogel film. The system is sensitive to the presence of copper ions at a concentration of 0.1 mg/L, which is sufficient for practical use. The insolubility of Rhodamine B in water during its immobilization in the volume of a photopolymerizable hydrogel film makes it possible to create a chemosensor that is stable at long exposures and is capable of sensing ultralow concentrations of impurities.

With the fast development of terahertz technology in medical diagnosis and monitoring, it has become important to investigate the application of THz radiation in the cancer treatment assessment during the therapy. In this paper, a buccal drug delivery system is studied as the first step towards this application. The drug delivery system is based on a gelatin-starch biopolymer matrix filled with plasticizing glycerol and various contents of reinforcing particles of bentonite clay. The biopolymers were subjected to morphology analysis using optical microscopy, analysis of mechanical tensile properties, and analysis of terahertz optical properties, followed by a theoretical approach of the experiment. The results show a visible effect of the bentonite content on both of the mechanical and terahertz optical properties of the biopolymer. These findings allow us to confirm the feasibility of using THz radiation for cancer assessment during therapies. The proposed biopolymer also has the potential to be applied as a substrate when carrying out in-vivo optical property measurement of biotissue in terahertz frequency range.

Methods of preparation of single-crystal 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST) films with a thickness of several micrometers, designed for electro-optic modulation, have been analyzed. Thin-film single crystals have been obtained, the shape and absorption spectrum of which confirm their crystal structure of the “red” DAST crystal form. Homogeneous luminescence in the polarization-contrast regime indicates their single crystallinity and uniform orientation. These materials are designed for intracavity modulation of laser radiation.

At present, due to the rapid development of THz technology in medical applications, it becomes urgent to develop stable test objects (phantoms) for calibration, optimization of the operation of devices, and verification of the research methods used. In this work, a five-component phantom has been developed based on water, glycerin, starch, bentonite, and gelatin, and it was shown that these phantoms can be used as indicators of the level of dehydration of the renal tumor tissue. The mechanical properties of the phantom were investigated, the dispersions of the refractive index and absorption coefficient of the biocomposite were determined in the range from 0.2 to 1 THz. To simulate the optical parameters of a phantom depending on the concentration of inclusions, an iterative method was developed and it was found that this method makes it possible to simulate the optical parameters of a phantom at low concentrations of bentonite. It is shown that in the structure of a five-component phantom, during fabrication, clusters of starch particles are formed, and the resonant interaction of the incident THz radiation with cluster particles leads to the excitation of whispering gallery modes.