https://doi.org/10.15407/iopt.2025.60.151

Optoelektron. napìvprovìd. teh. 60, 151-166 (2025)

K. V.  Kostyukevych, R. V.  Khrystosenko

MODIFICATION OF PLASMON METAL SURFACE PROPERTIES FOR THIN FILM BIOCHEMICAL SENSORS USING SULPHUR-CONTAINING MOLECULES

The work investigated the features of the formation and properties of monolayer films of sulfur-containing molecules of inorganic and organic origin on the gold surface of the SE SPR sensor for surface protection, stabilization of the properties of the metal film, and its adaptation to the adsorption of biological molecules. The process of forming a reactively inert coating (gold sulfide – AuxSy) for non-destructive physical adsorption of biomolecules onto the surface of a gold film was studied. It was shown (based on resonant SPR curves and the specific reaction of soybean trypsin inhibitor (SIT) – enzyme trypsin (Tp)) that under the action of reactive annealing of a polycrystalline gold film in a hydrogen sulfide (H2S) atmosphere for 15 hours, a dense monolayer of AuxSy is formed. The formation process is accompanied by the reconstruction of the gold surface, which stabilizes the characteristics of the SPR transducer and creates a boundary with less surface roughness and non-destructive properties for the physical adsorption of biologically active molecules. The feasibility of using organic films of dodecanethiol HS(CH2)11CH3, obtained by the method of self-organization of molecular (SOM) ensembles from solution, for protecting the working surface of the sensor, stabilizing the properties of the metal film, and adapting it to the adsorption of biological molecules is shown. In order to increase the speed of molecular binding, as well as the amplitude of the sensor response by increasing the area of the sensitive surface, a method of oriented fixation of receptor molecules in their natural, in a state undeformed by interaction with the metal inside the three-dimensional structure of the polysaccharide hydrogel – dextran, which was fixed on the gold surface using a thiol layer. The method of layer-by-layer deposition from aqueous solutions was used to form an inorganic five-layer film of copper (II) aminopentacyanoferrate (Cu3[Fe(CN)5NH3]2) on a COM-derived gold surface for the purpose of oriented immobilization of antibodies against human fibrinogen. It has been demonstrated that the use of this modification increases the response to the presence of fibrinogen in the sample by almost twofold. Another idea for using organic molecules called mercaptans, sulfur-containing molecules of various lengths and structures, was to create selective binding conditions for selected molecules using the molecular imprinting method. A method for forming an organic monolayer matrix on the surface of a gold film for molecular recognition of not very large molecules of barbituric acid C4H4O3N2 has been proposed and implemented. The matrix was obtained by the method of random co-adsorption of a mixture of dodecanethiol HS(CH2)11CH3 and thiobarbituric acid C4H4O2N2S from solution. It is shown that the mechanism that determines the selectivity of the interaction is the formation of fingerprints of analyte molecules in the surface organic layer, which allows the detection of barbituric acid against the background of its chemical analogue - veronal C8H12O3N2. To form a defect-free nanomolecular architecture of a self-organized coating on the surface of the CE sensors of the SPR, a low-temperature annealing technology (120 °C for 30 minutes) is proposed, which leads to smoothing of the small-scale relief of the gold surface and obtaining optimal parameters of the resonance curve.

Keywords: surface plasmon resonance, sulfur-containing molecules, metal surface of the sensing element, protection, stabilization, biocompatibility, functionalization.