DEVELOPMENT OF A TECHNIQUE FOR STUDYING TRIMETHYLAMINE OXIDE SOLUTIONS USING PLANAR SERS STRUCTURES

Novikov D.V.; Latipov E.V.; Dubkov S.V.; Savitskiy A.I.; Bandarenka H.V.; Bestavashvili Af.A.; Kopylov P.Yu.; Gromov D.G.

i l St. Petersburg Polytechnic University Journal. Physics and Mathematics. 2022 Vol. 15, No. 3.1 Научно-технические ведомости СПбГПУ. Физико-математические науки. 15 (3.1) 2022

Conference materials UDC 543.421/.424

DOI: https://doi.org/10.18721/JPM.153.141

Development of a technique for studying trimethylamine oxide solutions using planar SERS structures

D. V. Novikov 1 E. V. Latipov 2 , S. V. Dubkov 1 , A. I. Savitskiy 3 , H. V. Bandarenka 4 Af. A. Bestavashvili 5 , P. Yu. Kopylov 5 , D. G. Gromov 1

1 National Research University of Electronic Technology, Moscow, Russia;

2 Institute of Nanotechnology of Microelectronics RAS, Moscow, Russia;

3 5Scientific-Manufacturing Complex «Technological Centre», Moscow, Russia;

4 Belorussian State University of informatics and radioelectronic, Minsk, Belarus;

5 I.M. Sechenov First Moscow State Medical University, Moscow, Russia

H [email protected]

Abstract: This work is devoted to revealing the parameters of preparing SERS substrates for studying a low concentration trimethylamine oxide (TMAO) solution by Raman spectroscopy. A study was made of the effect of treatment with a 3,5% HCl solution, deionized water, and isopropanol vapor of planar surface enhance Raman spectroscopy (SERS) structures on the resulting Raman spectra of TMAO. We used a SERS substrate representing a multilayer structure: a mirror silver layer, a thin dielectric SiO2 insulating layer, and an array of plasmonic Ag nanoparticles about 25 nm in size. The influence of the duration of the substrate soaking in the analyte solution on the quality of the Raman spectra was established. Raman studies of SERS substrates with TMAO were carried out using 532 and 785 nm lasers.

Keywords: nanoparticles, silver, trimethylamine oxide, SERS

Funding: This work was supported by State Assignment for 2020-2022 no. FSMR-2020-0018.

Citation: Novikov D. V., Latipov E. V., Dubkov S. V., Savitskiy A.I., Bandarenka H. V., Bestavashvili Af. A., Kopylov P. Yu., Gromov D. G., Development of a technique for studying trimethylamine oxide solutions using planar SERS structures. St. Petersburg State Polytechnical University Journal. Physics and Mathematics. 15 (3.1) (2022) 243-247. DOI: https://doi. org/10.18721/JPM.153.141

This is an open access article under the CC BY-NC 4.0 license (https://creativecommons. org/licenses/by-nc/4.0/)

Материалы конференции УДК 543.421/.424

DOI: https://doi.org/10.18721/JPM.153.141

Разработка методики исследования растворов триметиламин оксида с использованием планарных ГКР-структур

Д. В. Новиков 1 н, Е. В. Латипов 2 , С. В. Дубков 1 , А. И. Савицкий 3 , А. В. Бондаренко 4 , А. А. Беставашвили 5 , Ф. Ю. Копылов 5 , Д. Г. Громов 1 1 Национальный исследовательский университет «МИЭТ», г. Москва, Россия; 2 Институт нанотехнологий микроэлектроники РАН, г. Москва, Россия; 3 Научно-производственный комплекс «Технологический центр», г. Москва, Россия; 4 Белорусский государственный университет информатики и радиоэлектроники, г. Минск, Беларусь; 5 Первый Московский государственный медицинский университет имени И. М. Сеченова, г. Москва, Россия;

н [email protected]

© Novikov D. V., Latipov E. V., Dubkov S. V., Savitskiy A.I., Bandarenka H. V., Bestavashvili Af. A., Kopylov P. Yu., Gromov D. G., 2022. Published by Peter the Great St.Petersburg Polytechnic University.

Аннотация. Данная работа посвящена выявлению параметров подготовки ГКР-подложек для исследования раствора триметиламин оксида (ТМАО) малой концентрации методом Рамановской спектроскопии. Было проведено исследование влияния обработки 3,5% (масс.) раствором HCl , деионизованной водой и парами изопропанола планарных структур гигантского комбинационного рассеяния (ГКР) на получаемые спектры ТМАО. В работе использовалась ГКР-подложка, представляющая многослойную структуру: зеркальный серебряный слой, тонкий диэлектрический слой-изолятора SiO2, массив плазмонных наночастиц Ag размером порядка 25 нм. Установлено влияние длительности вымачивания подложки в растворе аналита на качество рамановских спектров. Рамановские исследования ГКР-подложек с ТМАО производились с использованием лазеров 532 и 785 нм.

Ключевые слова: наночастицы, серебро, триметиламин оксид, гигантское комбинационное рассеяния

Финансирование: Работа выполнена в рамках государственного задания 2022-2020 гг. соглашение FSMR-2020-0018.

Ссылка при цитировании: Новиков Д. В., Латипов Е. В., Дубков С. В., Савицкий А. И., Бондаренко А. В., Беставашвили А. А., Копылов Ф. Ю., Громов Д. Г. Разработка методики исследования растворов триметиламин оксида с использованием планарных ГКР-структур // Научно-технические ведомости СПбГПУ. Физико-математические науки. 2022. Т. 15. № 3.1. С. 243-247. DOI: https://doi.org/10.18721/JPM.153.141

Статья открытого доступа, распространяемая по лицензии CC BY-NC 4.0 (https:// creativecommons.org/licenses/by-nc/4.0/)

Introduction

Today, the medical industry needs faster, more sensitive, and more accurate methods for analyzing biological samples. Effective methods have already been found to detect and determine the concentration for most components of human blood (cells, large proteins, inorganic salts) [1]. However, there are biomarkers that require long and painstaking analysis for their detection. One such substance is trimethylamine oxide. The risk of atherosclerosis, thrombosis and even stroke increase if the concentration of TMAO exceeds 2,25 цМ [2]. TMAO detection is possible using the High Performance Liquid Chromatography (HPLC) method [3]. HPLC has disadvantages that prevent the effective use of this method everywhere - a significant amount of human blood, complex equipment, high price, complicated sample preparation, analysis duration (more than 2 days) [3].

Surface enhanced Raman spectroscopy is an alternative method for diagnosing and detecting biomarkers [4]. This method is highly sensitive due to SERS-substrates based on nanoparticles of plasmonic metals (Au, Cu, Ag) [4]. The resulting spectrum makes it possible to judge the concentration of one or another component of the sample in the case of a study of a complex composition. However, high sensitivity may require compliance with a number of conditions: tight contact between the surface of the nanoparticle and the molecules under study; using a laser of a suitable wavelength; substrate pretreatment. Thus, there is an increased interest in determining these parameters for a quick and inexpensive study of TMAO in human blood.

In this work, we used planar SERS substrates based on a metal—dielectric mirror and an array of Ag nanoparticles. TMAO at a concentration of 10 mM used as the analyte. A weakly concentrated solution of hydrochloric acid and vapors of boiling isopropanol were used to treat the substrates. Lasers of two different wavelengths were used to study TMAO.

Materials and Methods

The SERS substrate was created in accordance with the method presented in earlier works [5]. Si(100) substrate with 300 nm SiO2 thickness was used as the basis for the SERS structure. The adhesive layer Cr 50 nm deposited by magnetron sputtering. Then, a 100 nm Ag reflective layer formed on the substrate by vacuum thermal evaporation. After that, the reflective layer coated

© Новиков Д. В., Латипов Е. В., Дубков С. В., Савицкий А. И., Бондаренко А. В., Беставашвили А. А., Копылов Ф. Ю., Громов Д. Г., 2022. Издатель: Санкт-Петербургский политехнический университет Петра Великого.

with 20 nm SiO2 as an insulator by the method of electron beam evaporation. The final step was the formation of an monolayer of uniformly distributed silver nanoparticles (NP) with average diameter 25 nm by annealing a 5 nm thin dispersed Ag film in vacuum at a temperature of 230 °C for 10 minutes. The size and distribution of nanoparticles were controlled by a Helios NanoLab 660 FEI scanning electron microscope. The formed monolayer of nanoparticles repeats the result obtained in previous work [5].

Before applying the analyte, some of the finished substrates were not processed. The second part was soaked in 3.5% (mass.) solution of hydrochloric acid (HCl) and washed in a slow flow of deionized water. The use of an identical technique by the authors in [6] showed that the treatment of Ag NPs in a weak solution of hydrochloric acid makes it possible to restore the intensity of the SERS signal for structures with different storage periods in air to the initial values. Thus, it can be assumed that the sulfide-oxide layer removed during the treatment from the surface of the nanoparticles is so small, so the treatment does not significantly affect the surface morphology. The third part treated with hot vapors of isopropyl alcohol 98.5%.

In this work TMAO with a concentration of 10 mM solutions used as analyte. The analyte was applied in two ways: by soaking the finished SERS structure in an analyte solution and by a drop from a dispenser. The substrates were soaked in the analyte solution for 5, 30, and 60 minutes. The substrates with the applied analyte dispenser dried in a fume hood at room temperature. Part of the samples with drops was covered with a cover slip for distribution and preservation in liquid form until the moment of examination.

The study was carried out on an inVia confocal microscope from Renishaw with the following parameters: wavelengths of 532 and 785 nm; laser power 5 mW; light spot diameter 4 ^m; spectrum accumulation time 60 s.

Results and Discussion

Considering the effect of soaking on untreated substrates (see Fig. 1) in the solution, we found that the most rational approach is to expose the sample for 30 minutes (Fig. 2). Increasing the exposure time to 60 minutes (in 2 times) increases the intensity of the SERS spectrum by only 18%. It should be noting that the soaking of the samples made it possible to distribute the analyte much more uniformly than when applied by a drop.

The study of the pretreatment effect showed that the use of dilute hydrochloric acid makes it possible to increase the efficiency of SERS substrates due to the removal of oxide and sulfide layers from silver nanoparticles that appear as a result of annealing and in a natural way, respectively (Fig. 3). Processing for 30 seconds and subsequent washing in a weak stream of deionized water for 10 seconds showed the following results: reduction of noise level; an increase in the intensity of characteristic TMAO peaks; reduction of the thermal decomposition [7]. The use of an isopropanol led to a drop in the quality of the spectrum to the level of noise.

1200

1000

=t 800 o

600

vt c 4>

^ 400 200 0

0 10 20 30 40 50 60 70 Soaking time, minute

Fig. 2. Dependence of the SERS intensity of the 7601 cm TMAO peak on the soaking time, wavelength 532 nm

Si (100) + SiOs 300 nm

Fig. 1. SERS-substrate scheme

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 Raman shift, cm1

Fig. 3. Raman spectra of TMAO without and with preliminary treatment of the SERS-substrate in 3,5% HCl solution for 30 s, wavelength 532 nm

The study of the influence of the treatment time on the intensity of the SERS spectrum showed that the optimal time for holding the substrate in the acid solution is from 15 to 30 seconds (Fig. 4). A further increase in the treatment time of the substrate leads to a rapid decrease in the intensity.

Fig. 5 demonstrates the influence of the laser wavelength on the efficiency of recording the Raman spectrum of TMAO. The TMAO spectra are of a high quality at 532 and 785 nm. The wavelength of 532 nm provides better visibility of more peaks, due to the greater plasmonic activity of Ag NPs in the blue-green region of the spectrum. The 785 nm wavelength provides better visibility of C-N and C-N-O bond peaks and reduces the thermal degradation of the analyte.

3500

3000

6 2500

° 2000

c 1500 £

^ 1000 500 0

0 10 20 30 40 50 60 70 Treatment time, seconds

Fig. 4. Dependence of the intensity of the 760 cm-1 peak on the treatment time, wavelength 532 nm

C-H

2V60

A

0 200 400 ¿00 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 Raman shift, cm'1

Fig. 5. TMAO spectra at different laser wavelengths, treatment time in acid solution ~30 s

Conclusion

In the course of the work, it was possible to establish the importance of a pre-treatment, soaking time and the laser used on the effectiveness of the study of TMAO. It was founding that the greatest effect in the study of TMAO using SERS-substrate based on Ag NPs will be provided that the following parameters are observed: treatment of the substrate in a 3,5% HCl solution for 15 to 30 seconds, followed by washing in a weak stream of deionized water; soaking time in TMAO solution for at least 30 minutes; using a 532 nm laser to search for C-H bonds of TMAO; using a 785 nm laser to search for C-N and C-N-O bonds of TMAO.

Acknowledgments

This work was supported by the State assignment 2020-2022 № FSMR-2020-0018.

REFERENCES

1. Encyclopedia Britannica. URL: https://www.britannica.com/science/blood-analysis. Accessed May 20, 2022.

2. Gatarek P., Kaluzna-Czaplinska J., Trimethylamine N-oxide (TMAO) in human health, EXCLI JOURNAL. 20 (2021) 301-319.

3. Leonardo P., Saleh A., Federico S., Alisdair R., Ultra-high-performance liquid chromatography highresolution mass spectrometry variants for metabolomics research, Nature Methods. 18 (2021) 733-746.

4. Cialla D., März A., Böhme R., Theil F., Weber K., Schmitt M., Popp J., Surface-enhanced Raman spectroscopy (SERS): progress and trends, Analytical and Bioanalytical Chemistry. 403 (2012) 27-54.

5. Dubkov S.V., Savitskiy A.I., Trifonov A.Yu., Yeritsyan G.S., Shaman Yu.P., Kitsyuk E.P., Tarasov A., Shtyka O., Ciesielski R., Gromov D.G., SERS in red spectrum region through array of Ag-Cu composite nanoparticles formed by vacuum-thermal evaporation, Optical Materials: X. 7 (2020) 100055.

6. Girel K.V., Panarin A.Y., Bandarenka H.V., Isic G., Bondarenko V.P., Terekhov S.N., Plasmonic silvered nanostructures on macroporous silicon decorated with graphene oxide for SERS-spectroscopy, Nanotechnology. 29 (2018) 395708.

7. Munroe K.L., Magers D.H., Hammer N.I., Raman Spectroscopic Signatures of Noncovalent Interactions Between Trimethylamine N-oxide (TMAO) and Water, The Journal ofPhysical Chemistry B. 23 (115) (2011) 7699-7707.

THE AUTHORS

NOVIKOV Denis V.

[email protected]

ORCID: 0000-0002-9518-1208

BANDARENKA Hanna V.

[email protected] ORCID: 0000-0003-4254-8261

LATIPOV Egor V.

[email protected]

ORCID: 0000-0002-6809-1952

[email protected] ORCID: 0000-0001-7551-1268

BESTAVASHVILI Afina A.

DUBKOV Sergey V. [email protected]