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Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials

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A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (10 July 2023) | Viewed by 24235

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Special Issue Editor

Prof. Dr. Won-Chun Oh

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Department of Advanced Materials Science & Engineering, Hanseo University, 46, Hanseo Ro, Haemi-myun, Seosan, Chungnam, Republic of Korea
Interests: carbon nanomaterials; nanocomposite; photocatalysis; energy materials
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Special Issue Information

Dear Colleagues,

We would like to invite all scientists, researchers and scholars in the field of multi-functional materials and applications, especially the participants of the 16th International Conference on Multi-functional Materials and Applications (ICMMA 2022, http://www.ijpcs.org/board/list.php), to submit their original research papers, short communications, reviews, and mini-reviews to this Special Issue of Nanomaterials, entitled “Multi-functional Materials and Applications”.

The conference topics and scope of this Special Issue cover all aspects of basic nanomaterials, catalysis, composites, electronics and biomaterials, and this issue will be divided into the follsowing main sections:

Nanomaterials related to design, synthesis and modifications;
Nanomaterials related to characterization;
Nanomaterials related to applications.

These detailed categories in the field of nanomaterials will be devoted to recent advances in the synthesis, modification, and characterization of sensors, as well as the energy conversion and storage of nanomaterials. This includes materials that may be used as biomaterials, the requirements they must meet, and problems that may be encountered in their use. Approaches from different fields of science (e.g., chemistry, engineering, human health and medicine) to the design, characterization, modification, and use of nanoscale biomaterials will be considered. Studies from these fields should focus on the latest research progress in all aspects related to composites and environmentally friendly multi-functional nanomaterials, including methods for their synthesis and characterization and their possible applications.

We kindly encourage you to submit a manuscript regarding one of the above topics to this Special Issue.

Prof. Dr. Won-Chun Oh
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Related Special Issue

Multi-Functional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials 2023 in Nanomaterials (1 article)

Published Papers (12 papers)

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Research

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12 pages, 2957 KiB

Open AccessEditor’s ChoiceArticle

Doping-Free Phosphorescent and Thermally Activated Delayed Fluorescent Organic Light-Emitting Diodes with an Ultra-Thin Emission Layer

by Eun-Bi Jang, Geun-Su Choi, Eun-Jeong Bae, Byeong-Kwon Ju and Young-Wook Park

Nanomaterials 2023, 13(16), 2366; https://doi.org/10.3390/nano13162366 - 18 Aug 2023

Viewed by 1425

Abstract

We report the electroluminescence (EL) characteristics of blue ultra-thin emissive layer (U-EML) phosphorescent (PH) organic light-emitting diodes (OLED) and thermally activated delayed fluorescence (TADF) OLED. A variety of transport layer (TL) materials were used in the fabricated OLEDs. The well-known FIrpic and DMAC-DPS were used with a thickness of 0.3 nm, which is relatively thicker than the optimal thickness (0.15 nm) of the blue phosphorescent ultra-thin emissive layer to ensure sufficient energy transfer. While FIrpic showed overall high efficiency in various TLs, DMAC-DPS exhibited three times lower efficiency in limited TLs. To clarify/identify low efficiency and to improve the EL, the thickness of DMAC-DPS was varied. A significantly higher and comparable efficiency was observed with a thickness of 4.5 nm, which is 15 times thicker. This thickness was oriented from the TADF itself, which reduces quenching in a triplet–triplet annihilation compared to the PH process. The thinner optimal thickness compared with ~30 nm of fluorescent OLEDs suggests that there still is quenching taking place. We expect that the efficiency of TADF U-EML OLEDs can be enhanced through further research on controlling the exciton quenching using multiple U-EMLs with spacers and a novel material with a high energy transfer rate (ΔE_S-T). Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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12 pages, 6374 KiB

Open AccessArticle

Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser

by Shin-Woo Kang, Eun-Jeong Bae, Young-Wook Park and Byeong-Kwon Ju

Nanomaterials 2023, 13(16), 2357; https://doi.org/10.3390/nano13162357 - 17 Aug 2023

Cited by 2 | Viewed by 1041

Abstract

In this study, various diffusers are applied to highly efficient ultra-thin emission layer (EML) structure-based blue phosphorescent organic light-emitting diodes (PHOLEDs) to improve the electroluminescence (EL) characteristics and viewing angle. To achieve highly efficient blue PHOLEDs, the EL characteristics of ultra-thin EML PHOLEDs with the various diffusers having different structures of pattern–shape (hemisphere/sphere), size (4~75 μm), distribution (surface/embedded), and packing (close-packed/random) were systematically analyzed. The diffusers showed different enhancements in the overall EL characteristics of efficiencies, viewing angle, and others. The EL characteristics showed apparent dependency on their structure. The external quantum efficiency (EQE) was enhanced mainly by following the orders of pattern, size, and shape. Following the pattern size, the EQE enhancement gradually increased; the largest-sized diffuser with a 75 μm closed-packed hemisphere (diffuser-1) showed a 1.47-fold EQE improvement, which was the highest. Meanwhile, the diffuser with a ~7 μm random embedded sphere with a low density (diffuser 5) showed the lowest 1.02-fold-improved EQE. The reference device with ultra-thin EML structure-based blue PHOLEDs showed a maximum EQE of 16.6%, and the device with diffuser 1 achieved a maximum EQE of 24.3% with a 5.1% wider viewing angle compared to the reference device without a diffuser. For the in-depth analysis, the viewing angle profile of the ultra-thin EML PHOLED device and fluorescent green OLEDs were compared. As a result, the efficiency enhancement characteristics of the diffusers show a difference in the viewing angle profile. Finally, the application of the diffuser successfully demonstrated that the EL efficiency and viewing angle could be selectively improved. Additionally, we found that it was possible to realize a wide viewing angle and achieve considerable EQE enhancement by further investigations using high-density and large-sized embedded structures of light-extraction film. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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10 pages, 2484 KiB

Open AccessArticle

Enhancing Light Extraction Efficiency in OLED Using Scattering Structure-Embedded DMD-Based Transparent Composite Electrodes

by Geun-Su Choi, Eun-Jeong Bae, Byeong-Kwon Ju and Young-Wook Park

Nanomaterials 2023, 13(15), 2253; https://doi.org/10.3390/nano13152253 - 05 Aug 2023

Cited by 1 | Viewed by 1438

Abstract

This study investigates the application of scattering structures to the metal layer in a DMD (Dielectric/Metal/Dielectric) configuration through plasma treatment. The purpose is to enhance the light extraction efficiency of organic light-emitting diodes (OLEDs). Different plasma conditions were explored to create scattering structures on the metal layer. The fabricated devices were characterized for their electrical and optical properties. The results demonstrate that the introduction of scattering structures through plasma treatment effectively improves the light extraction efficiency of OLEDs. Specifically, using O₂-plasma treatment on the metal layer resulted in significant enhancements in the total transmittance, haze, and figure of merit. These findings suggest that incorporating scattering structures within the DMD configuration can effectively promote light extraction in OLEDs, leading to enhanced overall performance and light efficiency. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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11 pages, 5566 KiB

Open AccessArticle

Fabrication of Flexible PDMS Films with Micro-Convex Structure for Light Extraction from Organic Light-Emitting Diodes

by Eun-Jeong Bae, Yeon-Sik Kim, Geun-Su Choi, Byeong-Kwon Ju, Dong-hyun Baek and Young-Wook Park

Nanomaterials 2023, 13(15), 2216; https://doi.org/10.3390/nano13152216 - 30 Jul 2023

Viewed by 1341

Abstract

In this study, we demonstrated organic light-emitting diodes (OLEDs) outcoupling with a flexible polydimethylsiloxane (PDMS) film with a micro-convex structure using the breath figure (BF) method. We can easily control the micro-convex pattern by adjusting the concentration of polystyrene and the humidity during the BF process. As process conditions to fabricate the micro-convex structure, polymer concentrations of 10, 20, 40, and 80 mg/mL and 60, 70, and 80% relative humidity were used. To evaluate the optical properties, we analyzed the transmission, diffusion, and electroluminescence with or without the micro-convex structure on the OLEDs. The shape and density of the micro-convex structure are related to its optical properties and outcoupling and we have experimentally demonstrated this. By applying a micro-convex structure, it achieved up to a 42% improvement in the external quantum efficiency compared to bare OLEDs (without any light extraction film). We expect the fabricated flexible light extraction film to be effective for outcoupling and applicable to flexible devices. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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15 pages, 7463 KiB

Open AccessFeature PaperArticle

Synthesis of LiDAR-Detectable True Black Core/Shell Nanomaterial and Its Practical Use in LiDAR Applications

by Suk Jekal, Jiwon Kim, Dong-Hyun Kim, Jungchul Noh, Min-Jeong Kim, Ha-Yeong Kim, Min-Sang Kim, Won-Chun Oh and Chang-Min Yoon

Nanomaterials 2022, 12(20), 3689; https://doi.org/10.3390/nano12203689 - 20 Oct 2022

Cited by 7 | Viewed by 2566

Abstract

Light detection and ranging (LiDAR) sensors utilize a near-infrared (NIR) laser with a wavelength of 905 nm. However, LiDAR sensors have weakness in detecting black or dark-tone materials with light-absorbing properties. In this study, SiO₂/black TiO₂ core/shell nanoparticles (SBT CSNs) were designed as LiDAR-detectable black materials. The SBT CSNs, with sizes of 140, 170, and 200 nm, were fabricated by a series of Stöber, TTIP sol-gel, and modified NaBH₄ reduction methods. These SBT CSNs are detectable by a LiDAR sensor and, owing to their core/shell structure with intrapores on the shell (ca. 2–6 nm), they can effectively function as both color and NIR-reflective materials. Moreover, the LiDAR-detectable SBT CSNs exhibited high NIR reflectance (28.2 R%) in a monolayer system and true blackness (L* < 20), along with ecofriendliness and hydrophilicity, making them highly suitable for use in autonomous vehicles. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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16 pages, 4742 KiB

Open AccessArticle

Hollow TiO₂ Nanoparticles Capped with Polarizability-Tunable Conducting Polymers for Improved Electrorheological Activity

by Seungae Lee, Jungchul Noh, Suk Jekal, Jiwon Kim, Won-Chun Oh, Hyung-Sub Sim, Hyoung-Jin Choi, Hyeonseok Yi and Chang-Min Yoon

Nanomaterials 2022, 12(19), 3521; https://doi.org/10.3390/nano12193521 - 08 Oct 2022

Cited by 5 | Viewed by 1829

Abstract

Hollow TiO₂ nanoparticles (HNPs) capped with conducting polymers, such as polythiophene (PT), polypyrrole (PPy), and polyaniline (PANI), have been studied to be used as polarizability-tunable electrorheological (ER) fluids. The hollow shape of TiO₂ nanoparticles, achieved by the removal of the SiO₂ template, offers colloidal dispersion stability in silicone oil owing to the high number density. Conducting polymer shells, introduced on the nanoparticle surface using vapor deposition polymerization method, improve the yield stress of the corresponding ER fluids in the order of PANI < PPy < PT. PT-HNPs exhibited the highest yield stress of ca. 94.2 Pa, which is 5.0-, 1.5-, and 9.6-times higher than that of PANI-, PPy-, and bare HNPs, respectively. The improved ER response upon tuning with polymer shells is attributed to the space charge contribution arising from the movement of the charge carriers trapped by the heterogeneous interface. The ER response of studied ER fluids is consistent with the corresponding polarizability results as indicated by the permittivity and electrophoretic mobility measurements. In conclusion, the synergistic effect of hollow nanostructures and conducting polymer capping effectively enhanced the ER performance. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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11 pages, 15633 KiB

Open AccessArticle

Improving Minutiae Image of Latent Fingerprint Detection on Non-Porous Surface Materials under UV Light Using Sulfur Doped Carbon Quantum Dots from Magnolia Grandiflora Flower

by David Nugroho, Won-Chun Oh, Saksit Chanthai and Rachadaporn Benchawattananon

Nanomaterials 2022, 12(19), 3277; https://doi.org/10.3390/nano12193277 - 21 Sep 2022

Cited by 8 | Viewed by 1816

Abstract

In this study, carbon quantum dots (CQDs) from Magnolia Grandiflora flower as a carbon precursor were obtained using a hydrothermal method under the optimized conditions affected by various heating times (14, 16, 18, and 20 min) and various electric power inputs (900–1400 W). Then, hydrogen sulfide (H₂S) was added to dope the CQDs under the same manner. The aqueous solution of the S-CQDs were characterized by FTIR, XPS, EDX/SEM, and TEM, with nanoparticle size at around 4 nm. Then, the as-prepared S-CQDs were successfully applied with fine corn starch for detection of minutiae latent fingerprints on non-porous surface materials. It is demonstrated that the minutiae pattern is more clearly seen under commercial UV lamps with a bright blue fluorescence intensity. Therefore, this research has proved that the S-CQDs derived from plant material have a better potential as fluorescent probes for latent fingerprint detection. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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10 pages, 3426 KiB

Open AccessArticle

Novel Nanoarchitectured Cu₂Te as a Photocathodes for Photoelectrochemical Water Splitting Applications

by Dong Jin Lee, G. Mohan Kumar, V. Ganesh, Hee Chang Jeon, Deuk Young Kim, Tae Won Kang and P. Ilanchezhiyan

Nanomaterials 2022, 12(18), 3192; https://doi.org/10.3390/nano12183192 - 14 Sep 2022

Cited by 3 | Viewed by 1624

Abstract

Designing photocathodes with nanostructures has been considered a promising way to improve the photoelectrochemical (PEC) water splitting activity. Cu₂Te is one of the promising semiconducting materials for photoelectrochemical water splitting, the performance of Cu₂Te photocathodes remains poor. In this work, we report the preparation of Cu₂Te nanorods (NRs) and vertical nanosheets (NSs) assembled film on Cu foil through a vapor phase epitaxy (VPE) technique. The obtained nano architectures as photocathodes toward photoelectrochemical (PEC) performance was tested afterwards for the first time. Optimized Cu₂Te NRs and NSs photocathodes showed significant photocurrent density up to 0.53 mA cm⁻² and excellent stability under illumination. Electrochemical impedance spectroscopy and Mott–Schottky analysis were used to analyze in more detail the performance of Cu₂Te NRs and NSs photocathodes. From these analyses, we propose that Cu₂Te NRs and NSs photocathodes are potential candidate materials for use in solar water splitting. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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13 pages, 2744 KiB

Open AccessArticle

Development of Novel Colorful Electrorheological Fluids

by Suk Jekal, Jiwon Kim, Qi Lu, Dong-Hyun Kim, Jungchul Noh, Ha-Yeong Kim, Min-Jeong Kim, Min-Sang Kim, Won-Chun Oh, Hyoung-Jin Choi and Chang-Min Yoon

Nanomaterials 2022, 12(18), 3113; https://doi.org/10.3390/nano12183113 - 08 Sep 2022

Cited by 4 | Viewed by 4071

Abstract

Herein, the electrorheological (ER) performances of ER fluids were correlated with their colors to allow for the visual selection of the appropriate fluid for a specific application using naked eyes. A series of TiO₂-coated synthetic mica materials colored white, yellow, red, violet, blue, and green (referred to as color mica/TiO₂ materials) were fabricated via a facile sol–gel method. The colors were controlled by varying the thickness of the TiO₂ coating layer, as the coatings with different thicknesses exhibited different light interference effects. The synthesized color mica/TiO₂ materials were mixed with silicone oil to prepare colored ER fluids. The ER performances of the fluids decreased with increasing thickness of the TiO₂ layer in the order of white, yellow, red, violet, blue, and green materials. The ER performance of differently colored ER fluids was also affected by the electrical conductivity, dispersion stability, and concentrations of Na⁺ and Ca²⁺ ions. This pioneering study may provide a practical strategy for developing new ER fluid systems in future. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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11 pages, 2820 KiB

Open AccessArticle

Assessment of Zinc-Bound Phosphate-Based Glass-Coated Denture-Relining Material with Antifungal Efficacy for Inhibiting Denture Stomatitis

by Sang-Hwan Oh, Yun-Sook Jung and Myung-Jin Lee

Nanomaterials 2022, 12(17), 3048; https://doi.org/10.3390/nano12173048 - 02 Sep 2022

Cited by 2 | Viewed by 1140

Abstract

This study investigated the surface properties, biocompatibility, and antifungal activity against Candida albicans of a denture-relining material coated with zinc-bound phosphate-based glass. First, zinc-bound phosphate-based glass was fabricated. A polymerized denture-relining disk was coated with zinc-bound phosphate-based glass (2%, 4%, and 6%). The surface properties of the control and experimental groups were measured, including the wettability, microhardness, color difference, and gloss. The biocompatibility was evaluated using the MTT assay according to ISO 10993-5. The antifungal activity was investigated by counting the number of colony-forming units of Candida albicans. The results were analyzed using a one-way ANOVA and Tukey’s test (p = 0.05). The results of this study indicate that, despite the antimicrobial effect of zinc-bound phosphate-based glass, a coated denture-relining material does not degrade the surface properties and biocompatibility. Therefore, this novel material is considered promising for use as a dental material with antimicrobial properties that can potentially prevent denture stomatitis. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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12 pages, 4920 KiB

Open AccessArticle

CO Methanation over NiO-CeO₂ Mixed-Oxide Catalysts Prepared by a Modified Co-Precipitation Method: Effect of the Preparation pH on the Catalytic Performance

by Amar Bendieb Aberkane, María Pilar Yeste, Fayçal Djazi and Miguel Ángel Cauqui

Nanomaterials 2022, 12(15), 2627; https://doi.org/10.3390/nano12152627 - 30 Jul 2022

Cited by 8 | Viewed by 1744

Abstract

In this study, a series of NiO-CeO₂ mixed-oxide catalysts have been prepared by a modified co-precipitation method similar to the one used for the synthesis of hydrotalcites. The syntheses were carried out at different pH values (8, 9 and 10), in order to determine the influence of this synthetic variable on the properties of the obtained materials. These materials were characterized by using different techniques, such as TGA, XRD, ICP, N₂ adsorption-desorption isotherms, H₂ temperature-programmed reduction (H₂-TPR), and electron microscopy, including high-angle annular dark-field transmission electron microscopy (HAADF-TEM) and EDS. The characterization results revealed the influence of the preparation method, in general, and of the pH value, in particular, on the textural properties of the oxides, as well as on the dispersion of the Ni species. The catalyst prepared at a higher pH value (pH = 10) was the one that exhibited better behavior in the CO methanation reaction (almost 100% CO conversion at 235 °C), which is attributed to the achievement, under these synthetic conditions, of a combination of properties (metal dispersion, specific surface area, porosity) more suitable for the reaction. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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Review

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32 pages, 8859 KiB

Open AccessReview

Controlled Growth of Semiconducting ZnO Nanorods for Piezoelectric Energy Harvesting-Based Nanogenerators

by Shamsu Abubakar, Sin Tee Tan, Josephine Ying Chyi Liew, Zainal Abidin Talib, Ramsundar Sivasubramanian, Chockalingam Aravind Vaithilingam, Sridhar Sripadmanabhan Indira, Won-Chun Oh, Rikson Siburian, Suresh Sagadevan and Suriati Paiman

Nanomaterials 2023, 13(6), 1025; https://doi.org/10.3390/nano13061025 - 13 Mar 2023

Cited by 8 | Viewed by 3048

Abstract

Zinc oxide (ZnO) nanorods have attracted considerable attention in recent years owing to their piezoelectric properties and potential applications in energy harvesting, sensing, and nanogenerators. Piezoelectric energy harvesting-based nanogenerators have emerged as promising new devices capable of converting mechanical energy into electric energy via nanoscale characterizations such as piezoresponse force microscopy (PFM). This technique was used to study the piezoresponse generated when an electric field was applied to the nanorods using a PFM probe. However, this work focuses on intensive studies that have been reported on the synthesis of ZnO nanostructures with controlled morphologies and their subsequent influence on piezoelectric nanogenerators. It is important to note that the diatomic nature of zinc oxide as a potential solid semiconductor and its electromechanical influence are the two main phenomena that drive the mechanism of any piezoelectric device. The results of our findings confirm that the performance of piezoelectric devices can be significantly improved by controlling the morphology and initial growth conditions of ZnO nanorods, particularly in terms of the magnitude of the piezoelectric coefficient factor (d33). Moreover, from this review, a proposed facile synthesis of ZnO nanorods, suitably produced to improve coupling and switchable polarization in piezoelectric devices, has been reported. Full article

(This article belongs to the Special Issue Multifunctional Materials and Applications: Basic Nanomaterials, Catalysis, Composite, Electronic and Biomaterials)

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