Films formed by metals and phenols through a coordinative interaction have been extensively studied in previous years. We report the successful formation of MPN films from the phenolic compounds caffeic acid and lignosulfonate using Fe³⁺ ions for complexation. The likewise examined p-coumaryl alcohol showed some MPN film formation tendency, while for coniferyl alcohol and sinapyl alcohol, no successful film buildup could be observed. These newly formed films were compared to tannic acid-Fe³⁺ films as a reference. Film growth and degradation were tracked by using UV-vis absorption spectroscopy. The films were degradable under different conditions such as alkaline environments or in the presence of a strong chelator. Small hollow capsules with a diameter of 3 μm and thicknesses in the nanometer range were produced. Additionally, the prepared films showed varying colors and levels of wettability. By utilizing the films' coating properties, we successfully dyed human hair in various colors.

Coupling Raman and VIS spectroscopy enables the study of AgNP aggregations induced by surfactants.

Measuring refractive index (RI) changes of liquid samples is central to many sensing applications including flow injection analysis, liquid chromatography, biosensing and photothermal spectroscopy. Commercial refractive index detectors optimized for liquid chromatography suffer from a limited linear range and measurement rate, restricting their use largely to separation sciences. In contrast, microring resonators (MRR) integrated with low-volume microfluidics, offer enhanced performance by minimizing sample dilution during flow-through RI measurements and increased dynamic range. MRRs realized by modern photonic integrated circuitry (PIC) technology also have the potential to be used as transducers in more advanced sensing schemes. Here, we demonstrate a silicon nitride (Si₃N₄) MRR integrated into a low-volume microfluidic system as a compact, chip-scale RI detector capable of real-time operation under dynamic flow conditions. Two interrogation modalities were experimentally compared for flow-through liquid sensing using the same MRR for the first time: resonance wavelength scanning for wide-range refractive index detection, and fixed-wavelength probing on the resonance slope for high-speed measurements. Using glucose solutions as test samples, the device was benchmarked against a commercial RI detector, achieving a sensitivity of 113 nm/RIU and a sLOD of 2.3 × 10^–6 RIU (0.014 g/L glucose). To demonstrate the applicability of the developed RI-sensor for resolving transient RI peaks in realistic chromatographic flow conditions we also report its successful use in an isocratic separation of four sugars (sorbitol, fructose, glucose, and sucrose). These results highlight the potential of integrated Si₃N₄ MRRs as versatile, miniaturized transducers for quantitative, high-speed RI sensing in flow-based analytical systems.

Sugar production generates wastewater rich in dissolved solids and organic matter, and improper disposal poses severe environmental risks, exacerbates water scarcity, and creates regulatory challenges. Conventional treatment methods, such as evaporation and chemical precipitation, are energy-intensive and often ineffective at removing fine particulates and dissolved impurities. This study evaluates membrane-based separation as a sustainable alternative for water reclamation and sugar recovery from sugar industry effluents, focusing on replacing evaporation with membrane processes, ensuring high permeate quality, and mitigating membrane fouling. Cross-flow filtration experiments were conducted on a lab-scale membrane system at 70 °C to suppress microbial growth, comparing direct reverse osmosis (RO) of the raw effluent to an integrated ultrafiltration (UF)–RO process. Direct RO resulted in rapid membrane fouling. A tight UF (5 kDa) pre-treatment before RO significantly mitigated fouling and improved performance, enabling 28% water recovery and 79% sugar recovery, maintaining permeate conductivity below 0.5 mS/cm, sustaining stable flux, and reducing membrane blocking. Additionally, the UF and RO membranes were tested via SEM, EDS, and FTIR to elucidate the fouling mechanisms.