Enhancement of dielectric and conductive properties of Mn 2 O 3 nanoparticles in liquid crystal under argon radio frequency plasma

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A. Mohammadi, F. Baharlounezhad, A. Ranjkesh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7277224/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 07 Nov, 2025 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract In this study, the effects of Ar radio plasma on Mn 2 O 3 nanoparticles and their influence on the dielectric and electrical properties of doped nematic liquid crystal were investigated. The nanoparticles were plasma-treated at different times and then added to the liquid crystal. The size of the nanoparticles and the surface morphology changed with increasing plasma application time. According to the results, significant changes in dielectric anisotropy were observed, the highest value of which was obtained after 2 minutes of plasma treatment. Also, changes in the parallel and vertical components of the dielectric constant indicated the effect of the orientation of the nanoparticles and the structure of the liquid crystal under the influence of Ar plasma. The impedance results also showed a significant decrease in impedance and improvement in conductivity of the liquid crystal matrix with increasing plasma treatment time, which was consistent with the equivalent circuit modeling. This study shows that the use of Ar radio plasma can be considered as a method for optimizing the properties of doped liquid crystals with nanoparticles in electronic and optoelectronic applications. Physical sciences/Materials science Physical sciences/Nanoscience and technology Physical sciences/Optics and photonics Physical sciences/Physics Argon Plasma Anisotropy Impedance Liquid Crystal Nanoparticle Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction The study of liquid crystals has gained great importance in recent years due to their wide applications in advanced technologies such as electronic displays, sensors and smart materials. Due to their unique physical properties, which lie between the solid and liquid states, liquid crystals allow the design of materials with tunable optical and electrical properties. Recent research on the development of liquid crystals with optimal performance has played a key role in the advancement of modern technologies [ 1 – 5 ]. Several methods have been developed to improve the performance of liquid crystals, the most important of which is the addition of various dyes and nanoparticles. Similar to isotropic media, the addition of dyes and nanoparticles with different structure and size to anisotropic media such as liquid crystals can improve their optical, electrical and thermal properties. In addition, mechanical methods as applying electric and magnetic fields also play a significant role in increasing the efficiency and performance of liquid crystals [ 6 – 11 ]. Among the different types of nanoparticles, metal nanoparticles have attracted the attention of various researchers due to their unique physical and chemical properties. This group of nanoparticles is synthesized by various methods and is widely used in various industries such as oil, gas, and medicine [ 12 – 13 ]. Therefore, in order to increase the efficiency of this group of particles, optimizing the structure and size of these particles is an important and challenging issue. Among the various types of chemical methods that lead to environmental pollution, the use of modern, clean and environmentally friendly methods is of particular importance. Therefore, plasma science and related technologies have received much attention in recent years. Plasma science studies matter in ionized state, which consists of charged particles and is known as fourth state of matter. This state of matter has grained great importance in modern science and technology due to its complex behavior under the influence of electronic and magnetic fields and active chemical reactions. Plasma is high-energy conditions allows for precise control of surface and chemical reactions, which play s a key role in industrial application such as surface coating, cleaning, cutting, and synthesis of advanced materials [ 14 ]. The emergence of plasma was due to the need to develop new technologies in various industries and to be better understand natural phenomena that involve conditions that are very different from the usual states of mater. The widespread applications of plasma in areas such as semiconductor manufacturing, water purification, medicine, and environment have made plasma science an independent and thriving branch of material science. Also, the unique capabilities of plasma in the production and modification of nanomaterials have made it possible to control the structure and properties of nanoparticles. The combination of plasma and nanotechnology with plasma science led to produce, modify, and fictionalize nanostructures with high precision. Application of this combination include the synthesis of nanoparticle and production nanostructured coating s with improved mechanical and electronic properties. This technology has wide application in fields such as catalysis, sensors, targeted drug delivery, and modern medicine, and it allow for reduction the activation energy of chemical reactions and increasing of efficiency of nonchemical processes [ 14 – 20 ]. Despite extensive efforts in this field [ 21 – 25 ], there is no studies on the Ar plasma effects on the Mn 2 O 3 nanoparticles. Our goal in this work is to present a new method for controlling the dielectric anisotropy and impedance values of liquid crystal samples containing Mn 2 O 3 nanoparticles, which are influential parameters in the design of optical devices. For this purpose, initially, Mn 2 O 3 nanoparticles were exposed to Ar radio plasma at a certain temperature and pressure for different time intervals. Then, the treated nanoparticles were added to the ML-648 nematic liquid crystal in a certain weight percentage. In this case, the parallel and vertical components of dielectric constant were measured at different temperatures, followed by the dielectric anisotropy. Finally, the real and imaginary values of the electrical impedance of liquid crystal samples containing nanoparticles were investigated and measured at different frequencies. 2. Experimental 2.1. Materials The study employed ML-648 nematic liquid crystal and Mn₂O3 nanoparticles, both supplied by Merck. The liquid crystal's nematic to isotropic phase transition temperature, as specified by the manufacturer, is near 81°C. 2.2. Cell preparation In this work, both homotropic and planar liquid crystal cells were fabricated. The construction process involved carefully positioning the samples between two indium tin oxide (ITO) coated optical glass substrates, each with dimensions of 2 × 1.5 cm². Surface alignment was established by applying a polyvinyl alcohol (PVA), which was subsequently subjected to unidirectional rubbing to induce the desired molecular orientation. To promote homotropic alignment in the cell lecithin was employed. A Mylar spacer was introduced to ensure a uniform cell gap between the electrode interfaces. Finally, the cell assembly was sealed using an appropriate adhesive to secure the substrates and maintain structural integrity. 2.3. Characterizations The physicochemical properties of the nanoparticles were systematically characterized using a high-resolution field emission scanning electron microscope (SEM-JSM-7600F), enabling detailed morphological analysis. Crystallin structure were investigated via X-ray diffraction (XRD) employing a Siemens XRD-D5000 diffractometer, utilizing monochromatic Cu Kα with a wavelength of λ = 1.5418 °A. Electrochemical impedance spectroscopy (EIS) measurements were performed using an IviumStat.h potentiostat/galvanostat system. Dielectric characterization of the nematic liquid crystal systems doped with Mn₂O₃ nanoparticles was carried out using a precision LCR meter (VICTOR 4091C), integrated with a temperature -regulated sample chamber to ensure thermal stability during measurements. The LC-nanoparticle hybrid systems were confined Whitin capacitor-type cells, specifically engineered to support both planar and homotropic molecular alignments for comparative dielectric evaluation. Capacitance measurements were conducted as a function of temperature, both in the absence (reference cell) and presence of the doped liquid crystal medium. The dielectric permittivities parallel (ε ∥ ) and perpendicular (ε ⊥ ) were extracted using the following analytical expressions: $$\:{{\epsilon\:}}_{\parallel\:}=\frac{{\text{C}}_{\perp\:}}{{\text{C}}_{\circ\:}}$$ 1 $$\:{{\epsilon\:}}_{\perp\:}=\frac{{\text{C}}_{\parallel\:}}{{\text{C}}_{\circ\:}}$$ 2 Here, C ∥ and C ⊥ correspond to the measured capacitances when the director of the liquid crystal molecules is aligned parallel and perpendicular to the electrode surfaces, respectively, C 0 denotes the capacitance of the empty reference cell. The dielectric anisotropy (Δε), a key parameter indicative of the material's electro-optic responsiveness, was computed using: Δε = ε ∥ - ε ⊥ (3) 2.4. Plasma Setup According to Fig. 1 , Mn 2 O 3 powders were placed in a radio frequency (RF) plasma reactor for studying the plasam effects. The plasma generator (50W, 13.56 MHz radio frequency) coupled with a turn copper coil with a 2 mm external diameter installed around a reaction chamber as an electrode. This chamber was in the form of a cylindrical glass tube with a length and external diameter of 300 mm and 60 mm, respectively. Plasma was produced and exerted at 0.001 Torr by using vacuum rotary pump. The working gas was argon. 3. Results and discussions According to Fig. 1 , Mn 2 O 3 powders were placed in a radio frequency (RF) plasma reactor for studying the plasma effects. The plasma generator (50W, 13.56 MHz radio frequency) coupled with a turn copper coil with a 2 mm external diameter installed around a reaction chamber as an electrode. This chamber was in the form of a cylindrical glass tube with a length and external diameter of 300 mm and 60 mm, respectively. Plasma was produced and exerted at 0.001 Torr by using vacuum rotary pump. The working gas was argon. 3.1.Temperature-dependent dielectric constants ana dielectric anisotropy under the influence of Ar Plasma As can be seen in Fig. 2 , the parallel component of dielectric constant of the liquid crystal samples containing Mn 2 O 3 nanoparticles increases with increasing temperature of the samples, first increases, then decreases, and finally reaches a constant value un the isotropic phase after passing the transition temperature. The vertical component behaves in the opposite way, with increasing temperature, it shows a decreasing trend, then an increasing trend, and reaches a constant value after passing the transition temperature. The effect of temperature on the parallel and vertical components of dielectric constant of liquid crystal containing Mn 2 O 3 nanoparticles can be described based on the changes in the order parameter and molecular polarizability. Increasing temperature reduces the long-range order of molecules, the parallel component of the dielectric constant initially increases due to increased molecular mobility and polarizability in the direction of the length of the molecules, but near the transition temperature in the isotropic phase, the sudden decrease in the order parameter causes this component to decrease and finally reaches a constant value in the isotropic phase. In contrast, the vertical component of the dielectric constant shows the opposite behavior with temperature change due to the decrease in the vertical polarizability and limitation of molecular oscillations in the direction perpendicular to the long molecular axis. Next, in order to control the dielectric constant changes, Mn 2 O 3 nanoparticles were exposed to Ar plasma for 2,7, and 14 minutes. Then, they were added to the nematic liquid crystal at a weight percentage of 0.5. According to the results obtained XRD (Fig. 3 ), the intensity of the peaks and their widths are affected by increasing the duration of exposure of the nanoparticles to the plasma. Thus, using the Scherr equation [ 27 ], the size of the crystals under plasma showed that initially the size of the nanoparticles was about 31.95 nm. By applying plasma for 2,7 and 14, respectively, the size of the nanoparticles reached 31.28, 32 and 31.24 nm. Thus, the size of the nanoparticles under the influence of plasma not show a regular trend, it initially decreases and increases with the application of plasma for 7 minutes and decreases again with the application of plasma for 14 minutes. Figure 4 shows that in addition to particle size, surface morphology also changes with the application of Ar plasma at different times. In general, Ar radio frequency, by applying ionization energy and electromagnetic radiation to the surface of Mn 2 O 3 , remove impurities, and activate surface centers, which directly affect the dispersion and distribution of nanoparticles in the nematic liquid crystal matrix. Theses surface modifications increase the local polarizability and improve the electrostatic interactions between nanoparticles and liquid crystal molecules, especially in the direction parallel to the long axis of the molecules, which has a higher intrinsic polarizability. Thus, Ar plasma causes the greatest increase in the parallel component of the dielectric constant at short times (2 min), because the optimal surface modification and uniform dispersion of nanoparticles maximize the polarizability in this direction. With increasing radio plasma time, relative aggregation of nanoparticles and structural change may occur, which reduces positive effect of the short-term plasma in the parallel component. In contrast, the vertical component of the dielectric constant, which represents the polarization in the direction perpendicular to the long axis, is less sensitive to surface changes and nanoparticle distribution. Longer plasma causes modifications in the nanoparticles structure which ultimately leads to a gradual increase polarization in the vertical direction, although this increase is smaller the parallel component. This behavior is due to the limitation of the movement of molecules and nanoparticles in the vertical direction, the more irregular distribution and lower intensity of local electric fields in this direction. In this case, the difference between the parallel and perpendicular components can be used to determine the anisotropy changes of the positive dielectric constant. According to Fig. 5 , the maximum anisotropy values is due to the nanoparticle being exposed to plasma for 2 minutes. Therefore, Ar plasma facilitates control of the dielectric properties of nematic liquid crystals containing Mn 2 O 3 nanoparticles, which is important in electronic and optical applications. 3.2. Impedance spectroscopy study under the influence of Ar plasma As shown in Fig. 6 , both the real and imaginary parts of the impedance were measured at different frequencies of the applied Ac electric field using the spectroscopic impedance technique. According to Fig. 6 , the changes in the real and imaginary parts of impedance the impedance depend on the applied frequency and duration of Ar plasma application on the doped nanoparticle in the nematic liquid crystal under study. A comparison between the results obtained from impedance spectroscopy for the sample without plasma effects versus the sample caused by Ar plasma shows that plasma effects lead to spectral shifts. Despite the spectral shift, a similar trend of changes with frequency changes was observed in all liquid crystal samples. The real part values of impedance of liquid crystal samples containing Mn 2 O 3 nanoparticles gradually decrease with increasing frequency and finally asymptotically approach the horizontal axis. Although a relatively regular behavior was observed in the changes in the real part values, no such behavior was observed in the imaginary part. With increasing frequency, the values of the imaginary part of the impedance of the samples initially show an increasing trend, then a decreasing trend, and finally reach a constant value with increasing frequency. In this case, as the duration of argon plasma application increases, the values of the real and imaginary parts of the impedance gradually decrease. These changes at low frequencies can be caused by the interaction between liquid crystal molecules at the interface with the electric field, and at high frequencies by the interaction of the dipole moment in the bulk state with the electric field [ 26 ]. Furthermore, by plotting the values of imaginary part of the impedance in terms of the values of the real part, we can obtain the Cole-Cole curves. These curves, which consist of a semicircular part and a linear part, respectively, show the behavior of liquid crystals containing nanoparticles at high and low frequencies. In order to simulate the behavior of liquid crystal samples containing nanoparticles, an equivalent electrical circuit is constructed as shown in Fig. 7 , which consist of six components as follows: R CR : Indicates the specific resistance of external elements and electrode connections. R LC : Indicates the resistance of the bulk liquid crystal. C LC : Indicates the capacitance of the bulk liquid crystal. C DL : Double layer polarity caused by the accumulation of charges near the electrodes. W: Representation of the Warburg element to describe the drift of charged species in a doped liquid crystal system. According to the simulation with the equivalent circuit, the diameter and the edge of the semicircle of the Cole-Cole curves represent R LC and R CR , respectively. The straight line in the diagrams is also related to the changes of the parallel set W and C DL . As can be clearly seen in Fig. 4 , the symbols represent the experimental data and the solid curves represent the results obtained from the fitting based on the equivalent circuit. The values obtained for the best fit (with an error of less than 5%) are shown in Table 1 . The resistance values due to electrodes and connectors are almost constant as expected. According to the data in Table 1 , just as the diameter of the Cole-Cole curves decrease with increasing plasma application time in the samples under plasma, the R LC values also decrease with increasing Ar plasma application time. The results obtained show that by applying plasma to nanoparticles, the conductivity of the liquid crystal matrix increases. In addition, the capacitance of the liquid crystal matrix containing Mn 2 O 3 nanoparticles increases with the application of Ar plasma compared to the case without plasma effects. The highest value is related to the time of 14 minutes, which is proportional to the change in the values of the vertical component of dielectric constant with the application of plasma. The changes can be due to the interactions between liquid crystal molecules and nanoparticles, which change with the application of plasma effects. The values obtained for the double layer capacitance also increase with the application of plasma, which can be related to the different effects of plasma on the size nanoparticles and surface morphology at different application times. These results show that the magnitude of capacity at the interface at low frequencies is larger than the capacity of liquid crystal in the bulk. The irregular changes in the W values can be due to molecular interactions with different intensities in the presence and absence of plasma effects. As a result, by applying Ar plasma for a certain period of time, the impedance values of liquid crystal samples containing Mn 2 O 3 nanoparticles can be reduced and their conductivity can be increased. Table 1 Extracted equivalent circuit parameters obtained by fitting the impedance spectroscopy data of Mn₂O₃ nanoparticle-doped liquid crystal samples subjected to argon plasma treatment. Sample R LC (MΩ) C LC (nF) C DL (µF) W sr (MΩS − 0.5 ) LC + Mn 2 O 3 3.162 1.443 0.035 6.632 LC + Mn 2 O 3 t = 2 min 2.464 1.867 0.059 5.273 LC + Mn 2 O 3 t = 7 min 2.062 1.875 0.373 6.433 LC + Mn 2 O 3 t = 14 min 1.391 2.140 0.245 3.574 4. Conclusions The application of Ar radio frequency plasma to Mn 2 O 3 nanoparticles caused noticeable changes in the dielectric and electrical properties of the doped liquid crystal. The size of the nanoparticles did not show a regular trend in the time interval from 0 to 14 minutes, The maximum dielectric anisotropy was observed at 2 minutes after plasma treatment, which is due to changes in the orientation and distribution of nanoparticles in the liquid crystal matrix. The parallel component of the dielectric showed the highest value at this time, while the vertical component had less changes and its maximum was recorded at 14 minutes, which indicates the effect of plasma treatment on the behavior of the liquid crystal doped with Mn 2 O 3 . Electrically, increasing the plasma treatment time led to a decrease in impedance and an improvement in conductivity of samples in charge carriers in the liquid crystal system. The results of importance measurements are consistent with the equivalent circuit modeling and confirm the accuracy of the analyses. These findings emphasize that Ar radio plasma is an effective method for improving the anisotropic dielectric properties and conductivity of liquid crystals containing nanoparticles and has potential applications in the development of advanced electronic and optoelectronic materials. Declarations Consent for publication: Not applicable. Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding: No funding sources. Author Contribution All authors contributed to the study conception and design. Sample preparation was performed by M. A. Mohammadi and F. Baharlounezhad. Experimental analysis was performed by M. Khadem Sadigh. The first draft of the manuscript was written by M. Khadem Sadigh. Writing – review & editing of manuscript was performed by M. Khadem Sadigh and A. Ranjkesh. All authors read and approved the final manuscript. 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Cite Share Download PDF Status: Published Journal Publication published 07 Nov, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 26 Aug, 2025 Reviews received at journal 25 Aug, 2025 Reviews received at journal 22 Aug, 2025 Reviews received at journal 18 Aug, 2025 Reviewers agreed at journal 17 Aug, 2025 Reviewers agreed at journal 14 Aug, 2025 Reviewers agreed at journal 14 Aug, 2025 Reviewers invited by journal 14 Aug, 2025 Editor invited by journal 14 Aug, 2025 Editor assigned by journal 12 Aug, 2025 Submission checks completed at journal 11 Aug, 2025 First submitted to journal 02 Aug, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7277224","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":501920918,"identity":"165dca98-aff5-42aa-bfbc-2e5554a97770","order_by":0,"name":"Mahsa Khadem Sadigh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDUlEQVRIiWNgGAWjYFACHih9mIGN4QPDAbgIDy4NKFoYZ5Cm5QADGzMPkhacQLf97OEPPxjq5PmOs197bNt2R86c/ewBhh81DDLmDdi1mJ3JS5PsYThsOPMwT7lxbtszY8uevATGnmMMPDIHcGg5kGMGdMkBxg2HedKkc9sOJ244kGPAwNvAwCOBw2Fm598Yf/zDUGcP1mIJ0nL+jQHjX3xabuQYSPMwMCduOMx+TJoRpAUowozXlhtvzKRlDA4nA/3CJtlz7pmxwY13CYdljkngcViO8cc3FXW2feePP5P4UXZHzuB87sGHb2ps7HFpgQADEMFjAOcfYGDArwEK2B8Qo2oUjIJRMApGIAAAeglbs0HOZtwAAAAASUVORK5CYII=","orcid":"","institution":"University of Bonab","correspondingAuthor":true,"prefix":"","firstName":"Mahsa","middleName":"Khadem","lastName":"Sadigh","suffix":""},{"id":501920921,"identity":"ae8c7c71-8cd1-41cf-974f-9592c6a8351f","order_by":1,"name":"M. A. Mohammadi","email":"","orcid":"","institution":"University of Tabriz","correspondingAuthor":false,"prefix":"","firstName":"M.","middleName":"A.","lastName":"Mohammadi","suffix":""},{"id":501920922,"identity":"0c07d5d3-0fcd-463c-a443-ffc9911cc8ef","order_by":2,"name":"F. Baharlounezhad","email":"","orcid":"","institution":"University of Tabriz","correspondingAuthor":false,"prefix":"","firstName":"F.","middleName":"","lastName":"Baharlounezhad","suffix":""},{"id":501920923,"identity":"d6c4bb6b-796e-4934-a99a-135b35a82b91","order_by":3,"name":"A. Ranjkesh","email":"","orcid":"","institution":"J. Stefan Institute","correspondingAuthor":false,"prefix":"","firstName":"A.","middleName":"","lastName":"Ranjkesh","suffix":""}],"badges":[],"createdAt":"2025-08-02 09:38:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7277224/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7277224/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-24909-5","type":"published","date":"2025-11-07T15:56:54+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":89651418,"identity":"c8affd99-6eb3-4f77-aa1a-d6391d042b2d","added_by":"auto","created_at":"2025-08-22 09:49:02","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":56560,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the plasma generation and treatment setup.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/de2cee86114eb0f21d1a5b36.jpg"},{"id":89651417,"identity":"51e16746-df0e-4d6a-8cf5-8d31e4d6156c","added_by":"auto","created_at":"2025-08-22 09:49:02","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":98762,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature dependence of the parallel (ε\u003csub\u003e∥\u003c/sub\u003e) and perpendicular (ε\u003csub\u003e⊥\u003c/sub\u003e) components of the dielectric constant of liquid crystal samples subjected to argon plasma treatment at varying exposure durations.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/9c8029a124e91d299b267390.jpg"},{"id":89651421,"identity":"54ad5894-a07c-4603-8055-5c7c69429dab","added_by":"auto","created_at":"2025-08-22 09:49:02","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":62494,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffraction (XRD) patterns illustrating structural modifications in liquid crystal samples after exposure to argon plasma for different time intervals.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/be6f9d119c8d6838d805dfea.jpg"},{"id":89651419,"identity":"0c298e2d-2314-4aa9-8f81-123690980264","added_by":"auto","created_at":"2025-08-22 09:49:02","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":110256,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscopy (SEM) micrographs of liquid crystal samples treated with argon plasma at (a) t = 0 min, (b) t = 2 min, (c) t = 7 min, and (d) t = 14 min, showing morphological evolution over time.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/a7a00ee5673287e2ec17dac6.jpg"},{"id":89652560,"identity":"6c4579bf-c590-4a08-b10c-80d5b2c3d701","added_by":"auto","created_at":"2025-08-22 09:57:02","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":55964,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of dielectric anisotropy (Δε) as a function of temperature for liquid crystal samples under argon plasma irradiation at multiple exposure times.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/460157da433247fe8dcc6afd.jpg"},{"id":89652838,"identity":"eaada0a5-b566-4a5a-9e5d-34ab54448166","added_by":"auto","created_at":"2025-08-22 10:05:02","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":63441,"visible":true,"origin":"","legend":"\u003cp\u003eFrequency-dependent changes in the real and imaginary components of the impedance of liquid crystal samples exposed to argon plasma at different time intervals.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/097d2cf282b629dd9cbe3135.jpg"},{"id":89652564,"identity":"811ed755-04d3-4788-bdfb-724df3077aad","added_by":"auto","created_at":"2025-08-22 09:57:02","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":59872,"visible":true,"origin":"","legend":"\u003cp\u003eCole-Cole impedance plots of liquid crystal samples after argon plasma treatment for various durations.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/3288fe5cb076a9e0b355b1bf.jpg"},{"id":95563895,"identity":"53889fa6-a117-4796-845a-aebda93d99de","added_by":"auto","created_at":"2025-11-10 16:01:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1076985,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7277224/v1/a4b5a5b7-6bd4-4c51-83cb-1391fdc21ce6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Enhancement of dielectric and conductive properties of Mn 2 O 3 nanoparticles in liquid crystal under argon radio frequency plasma","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe study of liquid crystals has gained great importance in recent years due to their wide applications in advanced technologies such as electronic displays, sensors and smart materials. Due to their unique physical properties, which lie between the solid and liquid states, liquid crystals allow the design of materials with tunable optical and electrical properties. Recent research on the development of liquid crystals with optimal performance has played a key role in the advancement of modern technologies [\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Several methods have been developed to improve the performance of liquid crystals, the most important of which is the addition of various dyes and nanoparticles. Similar to isotropic media, the addition of dyes and nanoparticles with different structure and size to anisotropic media such as liquid crystals can improve their optical, electrical and thermal properties. In addition, mechanical methods as applying electric and magnetic fields also play a significant role in increasing the efficiency and performance of liquid crystals [\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Among the different types of nanoparticles, metal nanoparticles have attracted the attention of various researchers due to their unique physical and chemical properties. This group of nanoparticles is synthesized by various methods and is widely used in various industries such as oil, gas, and medicine [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Therefore, in order to increase the efficiency of this group of particles, optimizing the structure and size of these particles is an important and challenging issue. Among the various types of chemical methods that lead to environmental pollution, the use of modern, clean and environmentally friendly methods is of particular importance. Therefore, plasma science and related technologies have received much attention in recent years. Plasma science studies matter in ionized state, which consists of charged particles and is known as fourth state of matter. This state of matter has grained great importance in modern science and technology due to its complex behavior under the influence of electronic and magnetic fields and active chemical reactions. Plasma is high-energy conditions allows for precise control of surface and chemical reactions, which play s a key role in industrial application such as surface coating, cleaning, cutting, and synthesis of advanced materials [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The emergence of plasma was due to the need to develop new technologies in various industries and to be better understand natural phenomena that involve conditions that are very different from the usual states of mater. The widespread applications of plasma in areas such as semiconductor manufacturing, water purification, medicine, and environment have made plasma science an independent and thriving branch of material science. Also, the unique capabilities of plasma in the production and modification of nanomaterials have made it possible to control the structure and properties of nanoparticles. The combination of plasma and nanotechnology with plasma science led to produce, modify, and fictionalize nanostructures with high precision. Application of this combination include the synthesis of nanoparticle and production nanostructured coating s with improved mechanical and electronic properties. This technology has wide application in fields such as catalysis, sensors, targeted drug delivery, and modern medicine, and it allow for reduction the activation energy of chemical reactions and increasing of efficiency of nonchemical processes [\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18 CR19\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Despite extensive efforts in this field [\u003cspan additionalcitationids=\"CR22 CR23 CR24\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], there is no studies on the Ar plasma effects on the Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles. Our goal in this work is to present a new method for controlling the dielectric anisotropy and impedance values of liquid crystal samples containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles, which are influential parameters in the design of optical devices. For this purpose, initially, Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles were exposed to Ar radio plasma at a certain temperature and pressure for different time intervals. Then, the treated nanoparticles were added to the ML-648 nematic liquid crystal in a certain weight percentage. In this case, the parallel and vertical components of dielectric constant were measured at different temperatures, followed by the dielectric anisotropy. Finally, the real and imaginary values of the electrical impedance of liquid crystal samples containing nanoparticles were investigated and measured at different frequencies.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003eThe study employed ML-648 nematic liquid crystal and Mn₂O3 nanoparticles, both supplied by Merck. The liquid crystal's nematic to isotropic phase transition temperature, as specified by the manufacturer, is near 81\u0026deg;C.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Cell preparation\u003c/h2\u003e\u003cp\u003eIn this work, both homotropic and planar liquid crystal cells were fabricated. The construction process involved carefully positioning the samples between two indium tin oxide (ITO) coated optical glass substrates, each with dimensions of 2 \u0026times; 1.5 cm\u0026sup2;. Surface alignment was established by applying a polyvinyl alcohol (PVA), which was subsequently subjected to unidirectional rubbing to induce the desired molecular orientation. To promote homotropic alignment in the cell lecithin was employed. A Mylar spacer was introduced to ensure a uniform cell gap between the electrode interfaces. Finally, the cell assembly was sealed using an appropriate adhesive to secure the substrates and maintain structural integrity.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Characterizations\u003c/h2\u003e\u003cp\u003eThe physicochemical properties of the nanoparticles were systematically characterized using a high-resolution field emission scanning electron microscope (SEM-JSM-7600F), enabling detailed morphological analysis. Crystallin structure were investigated via X-ray diffraction (XRD) employing a Siemens XRD-D5000 diffractometer, utilizing monochromatic Cu Kα with a wavelength of λ\u0026thinsp;=\u0026thinsp;1.5418 \u0026deg;A. Electrochemical impedance spectroscopy (EIS) measurements were performed using an IviumStat.h potentiostat/galvanostat system. Dielectric characterization of the nematic liquid crystal systems doped with Mn₂O₃ nanoparticles was carried out using a precision LCR meter (VICTOR 4091C), integrated with a temperature -regulated sample chamber to ensure thermal stability during measurements. The LC-nanoparticle hybrid systems were confined Whitin capacitor-type cells, specifically engineered to support both planar and homotropic molecular alignments for comparative dielectric evaluation. Capacitance measurements were conducted as a function of temperature, both in the absence (reference cell) and presence of the doped liquid crystal medium. The dielectric permittivities parallel (ε\u003csub\u003e∥\u003c/sub\u003e) and perpendicular (ε\u003csub\u003e\u0026perp;\u003c/sub\u003e) were extracted using the following analytical expressions:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{{\\epsilon\\:}}_{\\parallel\\:}=\\frac{{\\text{C}}_{\\perp\\:}}{{\\text{C}}_{\\circ\\:}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{{\\epsilon\\:}}_{\\perp\\:}=\\frac{{\\text{C}}_{\\parallel\\:}}{{\\text{C}}_{\\circ\\:}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eHere, C\u003csub\u003e∥\u003c/sub\u003e and C\u003csub\u003e\u0026perp;\u003c/sub\u003e correspond to the measured capacitances when the director of the liquid crystal molecules is aligned parallel and perpendicular to the electrode surfaces, respectively, C\u003csub\u003e0\u003c/sub\u003e denotes the capacitance of the empty reference cell. The dielectric anisotropy (Δε), a key parameter indicative of the material's electro-optic responsiveness, was computed using:\u003c/p\u003e\u003cp\u003eΔε\u0026thinsp;=\u0026thinsp;ε\u003csub\u003e∥\u003c/sub\u003e- ε\u003csub\u003e\u0026perp;\u003c/sub\u003e (3)\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Plasma Setup\u003c/h2\u003e\u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e powders were placed in a radio frequency (RF) plasma reactor for studying the plasam effects. The plasma generator (50W, 13.56 MHz radio frequency) coupled with a turn copper coil with a 2 mm external diameter installed around a reaction chamber as an electrode. This chamber was in the form of a cylindrical glass tube with a length and external diameter of 300 mm and 60 mm, respectively. Plasma was produced and exerted at 0.001 Torr by using vacuum rotary pump. The working gas was argon.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussions","content":"\u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e powders were placed in a radio frequency (RF) plasma reactor for studying the plasma effects. The plasma generator (50W, 13.56 MHz radio frequency) coupled with a turn copper coil with a 2 mm external diameter installed around a reaction chamber as an electrode. This chamber was in the form of a cylindrical glass tube with a length and external diameter of 300 mm and 60 mm, respectively. Plasma was produced and exerted at 0.001 Torr by using vacuum rotary pump. The working gas was argon.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1.Temperature-dependent dielectric constants ana dielectric anisotropy under the influence of Ar Plasma\u003c/h2\u003e\u003cp\u003eAs can be seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the parallel component of dielectric constant of the liquid crystal samples containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles increases with increasing temperature of the samples, first increases, then decreases, and finally reaches a constant value un the isotropic phase after passing the transition temperature. The vertical component behaves in the opposite way, with increasing temperature, it shows a decreasing trend, then an increasing trend, and reaches a constant value after passing the transition temperature. The effect of temperature on the parallel and vertical components of dielectric constant of liquid crystal containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles can be described based on the changes in the order parameter and molecular polarizability. Increasing temperature reduces the long-range order of molecules, the parallel component of the dielectric constant initially increases due to increased molecular mobility and polarizability in the direction of the length of the molecules, but near the transition temperature in the isotropic phase, the sudden decrease in the order parameter causes this component to decrease and finally reaches a constant value in the isotropic phase. In contrast, the vertical component of the dielectric constant shows the opposite behavior with temperature change due to the decrease in the vertical polarizability and limitation of molecular oscillations in the direction perpendicular to the long molecular axis. Next, in order to control the dielectric constant changes, Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles were exposed to Ar plasma for 2,7, and 14 minutes. Then, they were added to the nematic liquid crystal at a weight percentage of 0.5. According to the results obtained XRD (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), the intensity of the peaks and their widths are affected by increasing the duration of exposure of the nanoparticles to the plasma. Thus, using the Scherr equation [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], the size of the crystals under plasma showed that initially the size of the nanoparticles was about 31.95 nm. By applying plasma for 2,7 and 14, respectively, the size of the nanoparticles reached 31.28, 32 and 31.24 nm. Thus, the size of the nanoparticles under the influence of plasma not show a regular trend, it initially decreases and increases with the application of plasma for 7 minutes and decreases again with the application of plasma for 14 minutes. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows that in addition to particle size, surface morphology also changes with the application of Ar plasma at different times. In general, Ar radio frequency, by applying ionization energy and electromagnetic radiation to the surface of Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, remove impurities, and activate surface centers, which directly affect the dispersion and distribution of nanoparticles in the nematic liquid crystal matrix. Theses surface modifications increase the local polarizability and improve the electrostatic interactions between nanoparticles and liquid crystal molecules, especially in the direction parallel to the long axis of the molecules, which has a higher intrinsic polarizability. Thus, Ar plasma causes the greatest increase in the parallel component of the dielectric constant at short times (2 min), because the optimal surface modification and uniform dispersion of nanoparticles maximize the polarizability in this direction. With increasing radio plasma time, relative aggregation of nanoparticles and structural change may occur, which reduces positive effect of the short-term plasma in the parallel component. In contrast, the vertical component of the dielectric constant, which represents the polarization in the direction perpendicular to the long axis, is less sensitive to surface changes and nanoparticle distribution. Longer plasma causes modifications in the nanoparticles structure which ultimately leads to a gradual increase polarization in the vertical direction, although this increase is smaller the parallel component. This behavior is due to the limitation of the movement of molecules and nanoparticles in the vertical direction, the more irregular distribution and lower intensity of local electric fields in this direction. In this case, the difference between the parallel and perpendicular components can be used to determine the anisotropy changes of the positive dielectric constant. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the maximum anisotropy values is due to the nanoparticle being exposed to plasma for 2 minutes. Therefore, Ar plasma facilitates control of the dielectric properties of nematic liquid crystals containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles, which is important in electronic and optical applications.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Impedance spectroscopy study under the influence of Ar plasma\u003c/h2\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, both the real and imaginary parts of the impedance were measured at different frequencies of the applied Ac electric field using the spectroscopic impedance technique. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the changes in the real and imaginary parts of impedance the impedance depend on the applied frequency and duration of Ar plasma application on the doped nanoparticle in the nematic liquid crystal under study. A comparison between the results obtained from impedance spectroscopy for the sample without plasma effects versus the sample caused by Ar plasma shows that plasma effects lead to spectral shifts. Despite the spectral shift, a similar trend of changes with frequency changes was observed in all liquid crystal samples. The real part values of impedance of liquid crystal samples containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles gradually decrease with increasing frequency and finally asymptotically approach the horizontal axis. Although a relatively regular behavior was observed in the changes in the real part values, no such behavior was observed in the imaginary part. With increasing frequency, the values of the imaginary part of the impedance of the samples initially show an increasing trend, then a decreasing trend, and finally reach a constant value with increasing frequency. In this case, as the duration of argon plasma application increases, the values of the real and imaginary parts of the impedance gradually decrease. These changes at low frequencies can be caused by the interaction between liquid crystal molecules at the interface with the electric field, and at high frequencies by the interaction of the dipole moment in the bulk state with the electric field [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Furthermore, by plotting the values of imaginary part of the impedance in terms of the values of the real part, we can obtain the Cole-Cole curves. These curves, which consist of a semicircular part and a linear part, respectively, show the behavior of liquid crystals containing nanoparticles at high and low frequencies. In order to simulate the behavior of liquid crystal samples containing nanoparticles, an equivalent electrical circuit is constructed as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, which consist of six components as follows:\u003c/p\u003e\u003cp\u003eR\u003csub\u003eCR\u003c/sub\u003e: Indicates the specific resistance of external elements and electrode connections.\u003c/p\u003e\u003cp\u003eR\u003csub\u003eLC\u003c/sub\u003e: Indicates the resistance of the bulk liquid crystal.\u003c/p\u003e\u003cp\u003eC\u003csub\u003eLC\u003c/sub\u003e: Indicates the capacitance of the bulk liquid crystal.\u003c/p\u003e\u003cp\u003eC\u003csub\u003eDL\u003c/sub\u003e: Double layer polarity caused by the accumulation of charges near the electrodes.\u003c/p\u003e\u003cp\u003eW: Representation of the Warburg element to describe the drift of charged species in a doped liquid crystal system.\u003c/p\u003e\u003cp\u003eAccording to the simulation with the equivalent circuit, the diameter and the edge of the semicircle of the Cole-Cole curves represent R\u003csub\u003eLC\u003c/sub\u003e and R\u003csub\u003eCR\u003c/sub\u003e, respectively. The straight line in the diagrams is also related to the changes of the parallel set W and C\u003csub\u003eDL\u003c/sub\u003e. As can be clearly seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the symbols represent the experimental data and the solid curves represent the results obtained from the fitting based on the equivalent circuit. The values obtained for the best fit (with an error of less than 5%) are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The resistance values due to electrodes and connectors are almost constant as expected. According to the data in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, just as the diameter of the Cole-Cole curves decrease with increasing plasma application time in the samples under plasma, the R\u003csub\u003eLC\u003c/sub\u003e values also decrease with increasing Ar plasma application time. The results obtained show that by applying plasma to nanoparticles, the conductivity of the liquid crystal matrix increases. In addition, the capacitance of the liquid crystal matrix containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles increases with the application of Ar plasma compared to the case without plasma effects. The highest value is related to the time of 14 minutes, which is proportional to the change in the values of the vertical component of dielectric constant with the application of plasma. The changes can be due to the interactions between liquid crystal molecules and nanoparticles, which change with the application of plasma effects. The values obtained for the double layer capacitance also increase with the application of plasma, which can be related to the different effects of plasma on the size nanoparticles and surface morphology at different application times. These results show that the magnitude of capacity at the interface at low frequencies is larger than the capacity of liquid crystal in the bulk. The irregular changes in the W values can be due to molecular interactions with different intensities in the presence and absence of plasma effects. As a result, by applying Ar plasma for a certain period of time, the impedance values of liquid crystal samples containing Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles can be reduced and their conductivity can be increased.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eExtracted equivalent circuit parameters obtained by fitting the impedance spectroscopy data of Mn₂O₃ nanoparticle-doped liquid crystal samples subjected to argon plasma treatment.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eR\u003csub\u003eLC\u003c/sub\u003e(MΩ)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC\u003csub\u003eLC\u003c/sub\u003e (nF)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eC\u003csub\u003eDL\u003c/sub\u003e(\u0026micro;F)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eW\u003csub\u003esr\u003c/sub\u003e(MΩS\u003csup\u003e\u0026minus;\u0026thinsp;0.5\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLC\u0026thinsp;+\u0026thinsp;Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.443\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.035\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.632\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLC\u0026thinsp;+\u0026thinsp;Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003cp\u003et\u0026thinsp;=\u0026thinsp;2 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.464\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.867\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.059\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.273\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLC\u0026thinsp;+\u0026thinsp;Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003cp\u003et\u0026thinsp;=\u0026thinsp;7 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.062\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.875\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.373\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.433\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLC\u0026thinsp;+\u0026thinsp;Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003cp\u003et\u0026thinsp;=\u0026thinsp;14 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.391\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.140\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.245\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e3.574\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe application of Ar radio frequency plasma to Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles caused noticeable changes in the dielectric and electrical properties of the doped liquid crystal. The size of the nanoparticles did not show a regular trend in the time interval from 0 to 14 minutes, The maximum dielectric anisotropy was observed at 2 minutes after plasma treatment, which is due to changes in the orientation and distribution of nanoparticles in the liquid crystal matrix. The parallel component of the dielectric showed the highest value at this time, while the vertical component had less changes and its maximum was recorded at 14 minutes, which indicates the effect of plasma treatment on the behavior of the liquid crystal doped with Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\u003cp\u003eElectrically, increasing the plasma treatment time led to a decrease in impedance and an improvement in conductivity of samples in charge carriers in the liquid crystal system. The results of importance measurements are consistent with the equivalent circuit modeling and confirm the accuracy of the analyses. These findings emphasize that Ar radio plasma is an effective method for improving the anisotropic dielectric properties and conductivity of liquid crystals containing nanoparticles and has potential applications in the development of advanced electronic and optoelectronic materials.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConsent for publication:\u003c/h2\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eNo funding sources.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed to the study conception and design. Sample preparation was performed by M. A. Mohammadi and F. Baharlounezhad. Experimental analysis was performed by M. Khadem Sadigh. The first draft of the manuscript was written by M. Khadem Sadigh. Writing \u0026ndash; review \u0026amp; editing of manuscript was performed by M. Khadem Sadigh and A. Ranjkesh. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData is provided within the manuscript or supplementary information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eM. khadem Sadigh, A. Ranjkesh, B. Hayatifar, Improving the nonlinear electro-optical responses of doped nematic liquid crystals with chiral dopants, Opt. Mater., 135 (2023) 113352. https://doi.org/10.1016/j.optmat.2022.113352\u003c/li\u003e\n\u003cli\u003eM. Khadem Sadigh, P. Naziri, A. Ranjkesh, M.S. Zakerhamidi, Relationship of pitch length of cholesteric liquid crystals with order parameter and normalized polarizability, Opt. 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Boston, MA: Springer US. https://doi.org/10.1007/978-1-4899-0148-4_3\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Argon Plasma, Anisotropy, Impedance, Liquid Crystal, Nanoparticle","lastPublishedDoi":"10.21203/rs.3.rs-7277224/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7277224/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, the effects of Ar radio plasma on Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles and their influence on the dielectric and electrical properties of doped nematic liquid crystal were investigated. The nanoparticles were plasma-treated at different times and then added to the liquid crystal. The size of the nanoparticles and the surface morphology changed with increasing plasma application time. According to the results, significant changes in dielectric anisotropy were observed, the highest value of which was obtained after 2 minutes of plasma treatment. Also, changes in the parallel and vertical components of the dielectric constant indicated the effect of the orientation of the nanoparticles and the structure of the liquid crystal under the influence of Ar plasma. The impedance results also showed a significant decrease in impedance and improvement in conductivity of the liquid crystal matrix with increasing plasma treatment time, which was consistent with the equivalent circuit modeling. This study shows that the use of Ar radio plasma can be considered as a method for optimizing the properties of doped liquid crystals with nanoparticles in electronic and optoelectronic applications.\u003c/p\u003e","manuscriptTitle":"Enhancement of dielectric and conductive properties of Mn 2 O 3 nanoparticles in liquid crystal under argon radio frequency plasma","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 09:48:58","doi":"10.21203/rs.3.rs-7277224/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-26T04:11:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-25T07:18:30+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-22T06:02:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-18T11:26:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"272319633579803930732595225362235367441","date":"2025-08-17T06:42:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"77795352257688007317708013089421757035","date":"2025-08-14T17:29:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"209754865409333355639109882812433222383","date":"2025-08-14T17:28:55+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-14T16:40:13+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-08-14T16:28:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-12T09:50:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-11T09:16:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-08-02T09:31:47+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8c9397a5-faa2-4617-bc0d-5bf3849896b0","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":53309499,"name":"Physical sciences/Materials science"},{"id":53309500,"name":"Physical sciences/Nanoscience and technology"},{"id":53309501,"name":"Physical sciences/Optics and photonics"},{"id":53309502,"name":"Physical sciences/Physics"}],"tags":[],"updatedAt":"2025-11-10T15:58:35+00:00","versionOfRecord":{"articleIdentity":"rs-7277224","link":"https://doi.org/10.1038/s41598-025-24909-5","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-11-07 15:56:54","publishedOnDateReadable":"November 7th, 2025"},"versionCreatedAt":"2025-08-22 09:48:58","video":"","vorDoi":"10.1038/s41598-025-24909-5","vorDoiUrl":"https://doi.org/10.1038/s41598-025-24909-5","workflowStages":[]},"version":"v1","identity":"rs-7277224","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7277224","identity":"rs-7277224","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}