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i i St. Petersburg Polytechnic University Journal: Physics and Mathematics. 2022 Vol. 15, No. 3.2 Научно-технические ведомости СПбГПУ. Физико-математические науки. 15 (3.2) 2022
Conference materials UDC 535-15
DOI: https://doi.org/10.18721/JPM.153.256
Photoluminescent a-NaYbF4:Er002Ce002Zn01 nanoparticles for bioimaging in visible and infrared ranges
E. M. Trifanova e, A. V. Koshelev, K. V. Khaydukov, I. V. Krylov, V. K. Popov
Federal Scientific Research Center "Crystallography and Photonics" RAS, Moscow, Russia
Abstract. Nowadays noninvasive optical technologies require multifunctional nanomarkers, that can perform photoluminescence in different ranges of spectrum to provide broad possibilities for bioimaging. Photoluminescent nanoparticles doped with rare earth elements meet these requirements and are very promising for biological tissue visualization. a-NaYbF4:Er0 02Ce0 02Zn01 nanoparticles were characterized, had narrow and intensive photoluminescent peaks. Experiments were carried out on visualization in the visible and IR ranges of the spectrum. It was shown that a long photoluminescence lifetime made it possible to use the method of time-gated luminescence imaging. Visualization experiments with phantoms of biotissue both 3.5% fat milk and distilled water showed that nanoparticles can be used for multipurpose bioimaging.
Keywords: Photoluminescent nanoparticles, bioimaging, biotissue transparency windows, time-gated luminescence imaging
Funding: The study was funded by the Ministry of Science and Higher Education of the Russian Federation within the State Assignment FSRC 'Crystallography and Photonics' of RAS and RFBR, Project 20-32-90218.
Citation: Trifanova E. M., Koshelev A. V., Krylov I. V., Khaydukov K. V., Popov V. K., Photoluminescent a-NaYbF4:Er0 02Ce0 02Zn01 nanoparticles for bioimaging in visible and infrared ranges, St. Petersburg State Polytechnica! University Journal. Physics and Mathematics. 15 (3.2) (2022) 306-310. DOI: https://doi.org/10.18721/JPM.153.256
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 535-15
DOI: https://doi.org/10.18721/JPM.153.256
Фотолюминесцентные наночастицы a-NaYbF4:Er002Ce002Zn01 для биоимиджинга в видимом и инфракрасном диапазонах
Е. М. Трифанова н, А. В. Кошелев, К. В. Хайдуков, И. В. Крылов, В. К. Попов Федеральный научно-исследовательский центр "Кристаллография и фотоника" РАН, г. Москва, Россия
Аннотация. В настоящее время для неинвазивных оптических технологий требуются многофункциональные наномаркеры, способные люминесцировать в различных диапазонах спектра, что обеспечивает широкие возможности для биоимиджинга. Фотолюминесцентные наночастицы, легированные ионами редкоземельных элементов, отвечают этим требованиям и весьма перспективны для визуализации биологических тканей. Наночастицы a-NaYbF4:Er0 02Ce0 02Zn01, демонстрирующие интенсивную фотолюминесценцию в широком спектральном диапазоне, выбраны в качестве объекта исследования. Эксперименты по визуализации в видимом и ИК-диапазонах спектра сквозь сильно рассеивающую среду (3,5% цельное коровье молоко) и дистиллированную воду показали, что наночастицы a-NaYbF4:Er0 02Ce0 02Zn01 могут быть использованы для мультифункционального биоимиджинга.
© Trifanova E. M., Koshelev A. V., Krylov I. V., Khaydukov K. V., Popov V. K., 2022. Published by Peter the Great St. Petersburg Polytechnic University.
Biophysics and medical physics
Ключевые слова: Фотолюминесцентные наночастицы, биоимиджинг, окна прозрачности биотканей, фотолюминесцентная визуализация с отложенной регистрацией сигнала
Финансирование: Работа выполнена при поддержке Министерства науки и высшего образования в рамках выполнения работ по Государственному заданию ФНИЦ «Кристаллография и фотоника» РАН и РФФИ (проект № 20-32-90218_Аспиранты).
Ссылка при цитировании: Трифанова Е. М., Кошелев А. В., Крылов И. В., Хайдуков К. В., Попов В. К. Фотолюминесцентные наночастицы a-NaYbF4:Er0 02Ce0 02Zn01 для биоимиджинга в видимом и инфракрасном диапазонах // Научно-технические ведомости СПбГПУ. Физико-математические науки. Т. 15. № 3.2. С. 306—310. DOI: https://doi.org/10.18721/JPM.153.256
Статья открытого доступа, распространяемая по лицензии CC BY-NC 4.0 (https:// creativecommons.org/licenses/by-nc/4.0/)
Introduction
Noninvasive optical technologies including NIR and SWIR regions of spectrum usually use three biotissue transparency windows (BTW): I-BTW (650-950 nm), II-BTW (1000-1350 nm), III-BTW (1500-1870 nm) for bioimaging. Biological tissue has deeper penetration depths according to local minimum of loss coefficient in these wavelength ranges compared with visible range of spectrum [1]. Technologies that use I-BTW and III-BTW attract significant interest due to high signal-to-noise ratio, high spatial and time resolution [2]. Biological tissues have different compositions, but almost all of them consist water [3]. Water has a high absorption coefficient in III-BTW, which can complicate visualization at these wavelengths [4]. Therefore, to implement bioimaging in several BTWs at once, depending on optical properties of a biological object under study, it is important to develop universal multimodal nanomarkers with several photoluminescence peaks in a wide spectral range. Inorganic fluoride nanocrystals, doped with lanthanide (Ln3+) ions, demonstrated the required spectral characteristics [5]. Compared with other luminophores (quantum dotes, fluorescent dyes and proteins) Ln3+ doped fluoride nanoparticles (NPs) have a number of advantages for bioimaging applications [6]. They demonstrate superior chemical and photosta-bility, narrow band and large luminescence shifts relative to excitation light [7]. Depending on the specific application, the luminescence characteristics of fluoride NPs can be varied by changing the nature of the host lattice and doping elements. NPs NaYbF4, co-doped with Er3+ and Ce3+ can be used in fast in vivo brain imaging in the IR region above 1500 nm [8]. Temperature dependent NIR emission band pairs in II-BTW and III-BTW can be received by doping NaGdF4 NPs with Ho3+/ Nd3+ or Er3+/Nd3+ [9]. NaYF4 nanocrystals doped with Yb3+ and Tm3+ ions have been successfully used for bioimaging of the ovarian cancer cells line at the wavelength of 1 = 800 nm corresponding to I-BTW [10]. Also, presence of a large number of metastable long-lived excited 4f-states of Ln3+ ions makes it possible to use such NPs for time-gated luminescence imaging. In the context of non-invasive optical technologies this method allows the laser excitation signal and autoluminescence with a short lifetime to decay before the signal from the NPs with a long lifetime is received [11].
In this work, we demonstrated the possibility of using Ln3+-doped a-NaYbF4 NPs, which exhibit high intensity up- (~650 nm) and down-conversion (~1530 nm) photoluminescence under 1 = 976 nm irradiation, as imaging instrument. Two visualization experiments were carried out: imaging through a strongly scattering medium (3.5% fat cow milk) and distilled water aiming to imitate scattering and absorption coefficient of biotissue. Our experiments showed broad perspective in multipurpose visualization with photoluminescent NPs and recommendations on the choice of the detecting range depending on specificity of the application.
Materials and Methods
Lanthanide doped a-NaYbF4:Er002Ce002Zn01 NPs were synthesized by thermolysis method. The phase composition of the obtained nanocrystals was studied using an X-ray powder diffrac-tometer Rigaku Miniflex 600 (radiation CuKa) in the range of angles 10° < 20 < 120° with 1° scan step. The phases were identified using the ICDD PDF-2 (2014). The unit-cell parameters were calculated by the Le Bail full-profile fitting (the Jana2006 software). А semiconductor ATC-laser
© Трифанова Е. М., Кошелев А. В., Крылов И. В., Хайдуков К. В., Попов В. К., 2022. Издатель: Санкт-Петербургский политехнический университет Петра Великого.
with radiation peak at X = 976 nm (Semiconductor Devices, Russia) was used to excite the NPs. The study of photoluminescence spectrum of NPs was carried out on a spectrofluorime-ter Fluorolog 3 (HJY, France). The photoluminescence lifetime was measured under excitation of the semiconductor laser in a pulsed mode. The excitation laser beam was divided by splitter ~20/80%. 20% went on a silicon photodetector APDF and the rest 80% - on photomultiplier (PMT, Hamamatsu, Japan). The PMT signal corresponding to the decay kinetics was recorded on a TDS 6804B high-speed oscilloscope (Tektronix Inc., United States). TEM analysis was performed on a Tecnai Osiris (FEI, Hillsboro, OR, USA) electron microscope operated at 200 kV.
Experimental samples were prepared as follows: two pieces (1x10 mm) of white paper were covered with the NPs. The paper pieces were placed on a quartz cuvette with a 0.7 mm gap between them. 3.5% fat cow milk was chosen as a strongly scattering medium and distilled water was chosen as a medium with high absorption coefficient at X = 1530 nm [4]. Quartz cuvettes with optical paths length of 1—11 mm were used for experiments with distilled water.
For visualization in the visible range, we used a custom-build imaging system with EMCCD camera (Raptor Photonics Incorporated, USA). PC with the software controlled laser galvanometer scanner (Ateco Technocenter, Russia) for precise aiming of the laser beam on the sample. The system of interference filters (Semrock, USA) was used to notch the exciting radiation off. For visualization in the IR range, we performed time-gated luminescence imaging, using InGaAs camera (Hamamatsu, Japan). A chopper wheel was controlled by MC2000B optical light modulator (Thorlabs, USA) and installed between the InGaAs camera and the sample. The laser was in a pulsed mode.
Results and Discussion
The XRD analysis results of a-NaYbF4:Er002Ce002Zn01 NPs are shown in Fig. 1a. The reflections on the X-ray diffraction pattern correspond to the cubic structure of a-NaYbF4 (space group Fm3m, a = 5.469(6) A). According to the TEM data, the obtained nanocrystals were monodisperse particles of irregular shape with an average size of 36 nm (Fig. 1,b).
The photoluminescent properties of NPs are due to successive absorption of photons by ytterbium ions and further resonant nonradiative energy transfer to erbium ions within the crystalline matrix. The photoluminescence spectrum of NPs is shown in Fig. 2,a. The spectrum exhibits luminescence peaks in the visible and IR ranges of the spectrum, which correspond to characteristic electronic transitions in Er3+ ion. Yb3+ ions populate the 2F5/2 excited state during absorption of IR radiation at X = 976 nm. Then this ion nonradiatively transfers this energy to closely spaced neighboring Er3+. The Er3+ ions populate the metastable 4Illj2 excited state, where it can participate in synchronous energy exchange with the neighboring excited Yb3+, so that Er3+ populate higher energy levels 4F7/2 and 2G7/2. From an excited states 2H9/2, 2H11/2/4S3/2, 4F9/2 it passes into a state 4I15/2 with the emission of photons with X = 407, 525, 540, 652 nm respectively. When interacting with Ce3+, a resonant population of levels of Er3+ occurs above 4I13/2. As a result, the NPs have an intense luminescence peak at X = 1530 nm (Fig. 2,b). We measured the photoluminescence lifetime. At X = 1530 nm, it is 5.7 ms, which is suitable for time-gated photoluminescence imaging.
a) b)
Fig. 1. X-ray diffraction pattern (a), TEM images and histograms of size distribution of a-NaYbF4:Er002Ce0 02Zn01 nanoparticles (b)
Fig. 3. Images of the samples obtained through a 1 mm layer of 3.5% fat milk in visible (a) and NIR (b) region and through a 4 mm layer of water in visible (c) and NIR (d) region
We obtained images of samples in the visible and IR ranges of the spectrum through 1 mm layer of 3.5% fat cow milk. In the first case gap between the pieces is not observed, it is impossible to separate the image of one paper band from the other (Fig. 3,a). In contrast to the image obtained at 1 = 1530 nm (Fig. 3,b). The two luminescent bands are clearly visible. This can be explained by the Mie scattering effect — greater the wavelength, less light is scattered [12].
Several experiments were carried out with distilled water. The results are shown in Fig. 3,c and 3,d. The thickness of the water layer was increased from 1 mm to 11 mm. After 4 mm layer of water, the image in the IR range disappears. This is due to the high absorption coefficient of water at 1 = 1530 nm ~103 cm-1, while at 1 = 652 it is only ~10-2 cm-1 [4]. In the visible range the image is preserved up to a layer 11 mm thick, the gap is clearly visible in all images.
Conclusion
Various visualization tasks sometimes require individual solutions. Therefore, it is so important to find universal multifunctional nanomarkers performing photoluminescent radiation in different ranges of the spectrum. Clear images of NPs were a-NaYbF4:Er002Ce002Zn01 on the surface the paper pieces obtained through media with different optical properties. It was shown that for visualization through a strongly scattering medium, the time-gated photoluminescence imaging in IR region of the spectrum was perfectly suitable due to the long photoluminescence lifetime (more than 5 ms) of the NPs. While the experiment with increasing the thickness of the water layer showed that there was a strong absorption of radiation at 1 = 1530 nm. Therefore, it is possible to conduct through a medium with a high water content at 1 < 700 nm. The a-NaYbF4:Er0 02Ce0 02Zn01 NPs can be used as multipurpose photoluminescent nanomarkers both in I-BTW and III-BTW region of the spectrum.
Acknowledgments
The study was funded by the Ministry of Science and Higher Education within the State assignment FSRC 'Crystallography and Photonics' RAS and RFBR according to the project 20-32-90218. The authors are grateful to D.N. Karimov, and E.V. Khaydukov for fruitful discussions.
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THE AUTHORS
TRIFANOVA Ekaterina
ORCID: 0000-0003-4320-6917
KHAYDUKOV Kirill [email protected] ORCID: 0000-0001-5898-2404
KOSHELEV Alexander
POPOV Vladimir
[email protected] ORCID: 0000-0002-2119-6992
ORCID: 0000-0002-9305-6964
KRYLOV Ivan V.
Received 15.07.2022. Approved after reviewing 18.07.2022. Accepted 19.07.2022.
© Peter the Great St. Petersburg Polytechnic University, 2022
