V.M. Dzhagan, Ya.V. Pirko, A.Yu. Buziashvili et al. https://doi.org/10.15407/ujpe67.1.80 V.M. DZHAGAN, 1 YA.V. PIRKO, 2 A.YU. BUZIASHVILI, 2 S.G. PLOKHOVSKA, 2 M.M. BOROVA, 2 A.I. YEMETS, 2 N.V. MAZUR, 1 O.A. KAPUSH, 1 V.O. YUKHYMCHUK 1 1 V.E. Lashkaryov Institute of Semiconductor Physics, Nat. Acad. of Sci. of Ukraine (41, Nauky Ave., Kyiv 03028, Ukraine; e-mail: dzhagan@isp.kiev.ua) 2 Institute of Food Biotechnology and Genomics, Nat. Acad. of Sci. of Ukraine (2a, Osypovs’kogo Str., Kyiv 04123, Ukraine) CONTROLLED AGGREGATION OF PLASMONIC NANOPARTICLES TO ENHANCE THE EFFICIENCY OF SERS SUBSTRATES A possibility of creating universal and effective SERS substrates via controlled aggregation of gold and silver colloidal nanoparticles (NPs) on substrates with a specially developed sur- face morphology has been demonstrated. Unlike the previous work on the development and research of SERS substrates, in which the enhancement was mainly realized on separate pro- truding nanoparticles or nanoislands, the change to the multilevel substrate structuring and the controlled aggregation of the deposited colloidal plasmonic NPs substantially increases the formation probability of hot spots and getting analyte molecules onto them. The efficiency of the proposed approach has been demonstrated for several organic analytes of various types, in particular, the R6G dye, the cysteine amino acid, and antibodies. Keywords: SERS substrates, Raman spectroscopy, R6G, biomolecules. 1. Introduction Despite that the possibility of registering a Raman spectrum from a single molecule has already been demonstrated [1], the number of works devoted to the study of vibrational spectra of various substances making use of the surface-enhanced (or giant) Ra- man scattering (SERS) method and by means of the direct study of the mechanisms of Raman enhance- ment has been steadily growing every year. It occurs due to several factors. Firstly, this is the necessity of obtaining a Raman signal from an extremely small amount of substance, which is realized by deposit- ing the molecules onto SERS substrates or by plas- monic enhancement of the Raman signal generated by them in solutions. Secondly, this is the necessity of understanding the features in the manifestations of the mechanisms of electromagnetic (EM) and chemi- cal enhancement of the Raman signal. Thirdly, this is the necessity of developing universal and relatively in- c ○ V.M. DZHAGAN, YA.V. PIRKO, A.YU. BUZIASHVILI, S.G. PLOKHOVSKA, M.M. BOROVA, A.I. YEMETS, N.V. MAZUR, O.A. KAPUSH, V.O. YUKHYMCHUK, 2022 expensive SERS substrates capable of enhancing the Raman signal from various substances. Nowadays the detection of extremely small amounts of the substance is a very urgent task in many domains of science and human life. As examples we can point to chemistry and pharmacology while synthesizing new substances, criminology, medicine at the early diagnosis of dangerous diseases (espe- cially cancer), biology, ecology, materials science, safety, and so forth [2–9]. The SERS process involves the complex interac- tion of three objects: photons, targeted molecules, and metal nanostructures forming the basis of SERS substrates. The latter can be classified into two main categories: structured metal surfaces and metal NPs precipitated from colloidal solutions [10–17]. The most important manifestation of the EM en- hancement of the SERS signal from the examined substances is a considerable growth of the electric field in which they are located, which occurs due to both the excitation of plasmons in nanostructured metals and the formation of so-called “hot spots” as a result of superposition of electric fields generated by several metal NPs arranged at a nanometer dis- 80 ISSN 2071-0194. Ukr. J. Phys. 2022. Vol. 67, No. 1