Natural polyphenolic compounds play a pivotal role in biological processes and exhibit notable antioxidant activity. Among these compounds, chlorogenic acid stands out as one of the most widespread and important polyphenols. The accurate detection of chlorogenic acid is crucial for ensuring the quality and classification of the raw materials used in its extraction, as well as the final products in the food, pharmaceutical, and cosmetics industries that contain this bioactive compound. Raman spectroscopy emerges as a powerful analytical tool, particularly in field applications, due to its versatility and sensitivity, offering both qualitative and quantitative analyses. By using the self-assembly of gold nanoparticles at liquid–liquid interfaces and the developed “aqua-print” process, we propose a facile and inexpensive route to fabricate enhanced substrates for surface-enhanced Raman spectroscopy with high reproducibility. To ensure substrate reliability and accurate molecule detection in SERS experiments, a benchmarking procedure was developed. This process involved the use of non-resonant rhodamine 6G dye in the absence of charge transfer and was applied to all synthesized nanoparticles and fabricated substrates. The latter revealed the highest enhancement factor of 4 × 10⁴ for 72 nm gold nanoparticles among nanoparticle diameters ranging from 14 to 99 nm. Furthermore, the enhanced substrate was implemented in the detection of chlorogenic acid with a concentration range from 10 μM to 350 μM, demonstrating high accuracy (R² > 99%). Raman mapping was employed to validate the good uniformity of the signal (the standard deviation was below 15%). The findings of this study were also supported by DFT calculations of the theoretical Raman spectra, demonstrating the formation of the chlorogenic acid dimer. The proposed method is strategically important for the development of the class of in-field methods to detect polyphenolic compounds in raw materials such as plants, extracted plant proteins, and polyphenolic compounds.

Properties of composite materials with polymer matrix and inorganic filler are affected by preparation methods and starting components’ properties. For example, filler powder particle size distribution, phase composition and presence/absence of dopants can greatly affect properties of resulting composites. The present research attempts to clarify the influence of synthetic CaCO₃ powder properties on alginate/CaCO₃ composite material preparation process. Composite materials in the form of granules, networks and films were created from suspensions of synthetic powders of calcium carbonates CaCO₃ in aqueous solutions of sodium alginate. Powders of calcium carbonates CaCO₃ were synthesized from 0.5 M aqueous solutions of calcium chloride CaCl₂ and aqueous solutions of potassium K₂CO₃ (at molar ratio Ca/CO₃ = 1), sodium Na₂CO₃ (at molar ratio Ca/CO₃ = 1), and ammonium (NH₄)₂CO₃ (at molar ratios Ca/CO₃ = 1 and Ca/CO₃ = 0.5) carbonates. Phase composition of powder synthesized from CaCl₂ and K₂CO₃ was presented by calcite. Phase composition of powders synthesized from other soluble carbonates included calcite and vaterite. The powder preparation protocol excluded the stage of synthesized powder washing for by-product removal. This preparation protocol provided preservation of reaction by-product in the synthesized powder at a very low level. The presence of NH₄Cl as a reaction by-product even in small quantities can be taken as a reason for visually observed subsequences of cross-linking reaction at the stage of suspensions preparation. Aqueous solution of sodium alginate and suspensions containing powders synthesized from potassium K₂CO₃ and sodium Na₂CO₃ carbonates demonstrated similar dependence of viscosities from shear rate. The presence of (NH₄)₂CO₃ in the powder synthesized at molar ratio Ca/CO₃ = 0.5 was the reason for the lower viscosity of the suspension in comparison with suspensions loaded with powders containing KCl, NaCl and (NH₄)₂Cl as reaction by-products due to decomposition of unstable (NH₄)₂CO₃ and gas phase formation. The presence of (NH₄)₂Cl in the powder synthesized at molar ratio Ca/CO₃ = 1 in contrast was a reason for the highest viscosity suspension in comparison with those under investigation. Additionally, (NH₄)₂Cl presence in synthetic powders shows the ability to facilitate partial dissolution of CaCO₃ providing a higher concentration of Ca²⁺ cations at the stage of suspension preparation, thus aiding the cross-linking process of alginate hydrogel. Granules, meshes and films were created via interaction of suspensions of calcium carbonates CaCO₃ in aqueous solutions of sodium alginate with 0.25 M aqueous solutions of calcium chloride CaCl₂ to provide the formation of matrix of composites via Ca-crosslinking of sodium alginate followed by washing and freeze drying under deep vacuum. The created composite materials in the form of granules, meshes and films based on Ca-cross-linked alginate and powders of synthetic calcium carbonate can be recommended for skin wound and bone defect treatment and drug delivery carriers.

Surface-enhanced Raman scattering (SERS) tags based on polymer microspheres (PMS) show significant promise for applications in liquid environments, particularly in the study of biological systems. The core principle of this fabrication method is to concentrate gold nanoparticles within a single point, with dimensions comparable to the diameter of the laser spot. These tags remain clearly visible in the solution and, owing to the formation of interparticle hot spots, yield enhanced SERS signals. In this work, we developed gold nanoparticle (AuNP) decorated polymer microspheres (PMS) for use as efficient SERS tags. A well-established layer-by-layer deposition technique was compared with nanoparticle aggregation from quasi-stable colloidal solution to fabricate SERS tags. The SERS performance of these AuNP-decorated PMS was evaluated using rhodamine 6G as a non-resonant model molecule. Structures fabricated by the aggregation method showed a higher surface filling factor (FF = 32%) and notably greater analytical enhancement (AEF of 1.4 × 10⁴), significantly outperforming those from layer-by-layer deposition (14% FF, 7.5 × 10³ AEF). Furthermore, the practical applicability of these SERS tags was validated through two applications: the quality assessment of motor oil in the non-aqueous environment and the quantitative analysis of 2,4-dinitrophenol in the aqueous solution. These results underscore the potential of the AuNP-decorated PMS SERS tags for diverse analytical and quality control applications.

Composite materials in form of granules, networks and films were created from sus-pensions of synthetic powders of calcium carbonates CaCO3 in aqueous solutions of sodium alginate. Powders of calcium carbonates CaCO3 were synthesized from 0.5M aqueous solutions of calcium chloride CaCl2 and aqueous solutions of potassium K2CO3 (at molar ratio Ca/CO3=1), sodium Na2CO3 (at molar ratio Ca/CO3=1), ammonium (NH4)2CO3 (at molar ratios Ca/CO3=1 and Ca/CO3=0.5) carbonates. Phase composition of powder synthesized from CaCl2 and K2CO3 was presented by calcite. Phase compo-sition of powders synthesized from other soluble carbonates included calcite and va-terite. The powder preparation protocol excluded the stage of by-product removing via synthesized powder washing providing their preservation at very low level. Presence of NH4Cl as reaction by-product even in small quantities can be taken as a reason vis-ually observed subsequences of cross-linking reaction at the stage of suspensions preparation. Aqueous solution of sodium alginate and suspensions containing powders synthesized from potassium K2CO3 and sodium Na2CO3 carbonates demonstrated the similar dependence of viscosities from share rate. Presence of (NH4)2CO3 in the powder synthesized at molar ratio Ca/CO3=0.5 was the reason of the lower viscosity of the suspension in comparison with suspensions loaded with powders containing KCl, NaCl and (NH4)2Cl as reaction by-products due to decomposition of unstable (NH4)2CO3 and gas phase formation. Presence of (NH4)2Cl in the powder synthesized at molar ratio Ca/CO3=1 in contrary was a reason of the highest viscosity suspension comparison with those under investigation. Granules, meshes and films were created via interaction of suspensions calcium carbonates CaCO3 in aqueous solutions of so-dium alginate with 0.25M aqueous solutions of calcium chloride CaCl2 to provide formation of matrix of composites via Ca-crosslinking of sodium alginate followed by washing and freeze drying under deep vacuum. Created composite materials in form of granules, meshes and films based on Ca-cross-linked alginate and powders of synthetic calcium carbonate can be recommended for the skin wounds and bone defects treatment, and drug delivery carriers.