Research

9 pages, 2259 KiB

Open AccessArticle

Synthesis and Characteristics of Double-Shell Mesoporous Hollow Silica Nanomaterials to Improve CO₂ Adsorption Performance

by Jong-tak Lee and Jae-Young Bae

Micromachines 2021, 12(11), 1424; https://doi.org/10.3390/mi12111424 - 19 Nov 2021

Cited by 3 | Viewed by 1827

Abstract

To improve the adsorption performance of carbon dioxide, which is considered the main culprit of greenhouse gases, the specific surface area and high pore volume of the adsorbing material should be considered. For a porous material, the performance of carbon dioxide adsorption is [...] Read more.

To improve the adsorption performance of carbon dioxide, which is considered the main culprit of greenhouse gases, the specific surface area and high pore volume of the adsorbing material should be considered. For a porous material, the performance of carbon dioxide adsorption is determined by the amine groups supporting capacity; the larger the pore volume, the greater the capacity to support the amine groups. In this study, a double-shell mesoporous hollow silica nanomaterial with excellent pore volume and therefore increased amine support capacity was synthesized. A core–shell structure capable of having a hollow shape was synthesized using polystyrene as a core material, and a double-shell mesoporous shape was synthesized by sequentially using two types of surfactants. The synthesized material was subjected to a sintering process of 600 degrees, and the N₂ sorption analysis confirmed a specific surface area of 690 m²/g and a pore volume of 1.012 cm³/g. Thereafter, the amine compound was impregnated into the silica nanomaterial, and then, a carbon dioxide adsorption experiment was conducted, which confirmed that compared to the mesoporous hollow silica nanomaterial synthesized as a single shell, the adsorption performance was improved by about 1.36 times. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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11 pages, 4450 KiB

Open AccessArticle

Improvement in Turn-Off Loss of the Super Junction IGBT with Separated n-Buffer Layers

by Ki Yeong Kim, Joo Seok Noh, Tae Young Yoon and Jang Hyun Kim

Micromachines 2021, 12(11), 1422; https://doi.org/10.3390/mi12111422 - 19 Nov 2021

Cited by 1 | Viewed by 2051

Abstract

In this study, we propose a super junction insulated-gate bipolar transistor (SJBT) with separated n-buffer layers to solve a relatively long time for carrier annihilation during turn-off. This proposition improves the turn-off characteristic while maintaining similar on-state characteristics and breakdown voltage. The electrical [...] Read more.

In this study, we propose a super junction insulated-gate bipolar transistor (SJBT) with separated n-buffer layers to solve a relatively long time for carrier annihilation during turn-off. This proposition improves the turn-off characteristic while maintaining similar on-state characteristics and breakdown voltage. The electrical characteristics of the devices were simulated by using the Synopsys Sentaurus technology computer-aided design (TCAD) simulation tool, and we compared the conventional SJBT with SJBT with separated n-buffer layers. The simulation tool result shows that turn-off loss (E_off) drops by about 7% when on-state voltage (V_on) and breakdown voltage (BV) are similar. V_on increases by about 0.5% and BV decreases by only about 0.8%. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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7 pages, 2722 KiB

Open AccessArticle

Growth and Drug Interaction Monitoring of NIH 3T3 Cells by Image Analysis and Capacitive Biosensor

by Gayoung Lee, Jaehun Jeong, Yeeun Kim, Dahyun Kang, Sooyong Shin, Jongwon Lee, Sung Ho Jeon and Moongyu Jang

Micromachines 2021, 12(10), 1248; https://doi.org/10.3390/mi12101248 - 14 Oct 2021

Cited by 6 | Viewed by 1743

Abstract

Capacitive biosensors are manufactured on glass slides using the semiconductor process to monitor cell growth and cell–drug interactions in real time. Capacitance signals are continuously monitored for each 10 min interval during a 48 h period, with the variations of frequency from 1 [...] Read more.

Capacitive biosensors are manufactured on glass slides using the semiconductor process to monitor cell growth and cell–drug interactions in real time. Capacitance signals are continuously monitored for each 10 min interval during a 48 h period, with the variations of frequency from 1 kHz to 1 MHz. The capacitance values showed a gradual increase with the increase in NIH 3T3 cell numbers. After 48 h of growth, 6.67 μg/mL puromycin is injected for the monitoring of the cell–drug interaction. The capacitance values rapidly increased during a period of about 10 h, reflecting the rapid increase in the cell numbers. In this study, we monitored the state of cells and the cell–drug interactions using the developed capacitive biosensor. Additionally, we monitored the state of cell behavior using a JuLi^TM Br&FL microscope. The monitoring of cell state by means of a capacitive biosensor is more sensitive than confluence measuring using a JuLi^TM Br&FL microscope image. The developed capacitive biosensor could be applied in a wide range of bio-medical areas; for example, non-destructive real-time cell growth and cell–drug interaction monitoring. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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9 pages, 1402 KiB

Open AccessArticle

Suppressed Transmission of Long-Range Surface Plasmon Polariton by TE-Induced Edge Plasmon

by Guhwan Kim and Myunghyun Lee

Micromachines 2021, 12(10), 1198; https://doi.org/10.3390/mi12101198 - 30 Sep 2021

Viewed by 1840

Abstract

Work on controlling the propagation of surface plasmon polaritons (SPPs) through the use of external stimuli has attracted much attention due to the potential use of SPPs in nanoplasmonic integrated circuits. We report that the excitation of edge plasmon by TE-polarized light passing [...] Read more.

Work on controlling the propagation of surface plasmon polaritons (SPPs) through the use of external stimuli has attracted much attention due to the potential use of SPPs in nanoplasmonic integrated circuits. We report that the excitation of edge plasmon by TE-polarized light passing across gapped-SPP waveguides (G-SPPWs) leads to the suppressed transmission of long-range SPPs (LRSPPs) propagating along G-SPPWs. The induced current density by highly confined edge plasmon is numerically investigated to characterize the extended radiation length of decoupled LRSPPs by the TE-induced edge plasmon. The suppressed transmission of LRSPPs is confirmed using the measured extinction ratio of the plasmonic signals which are generated from the modulated optical signals, when compared to the extended radiation length calculated for a wide range of the input power. It is also shown that LRSPP transmission is sensitive to the excited power of edge plasmon in the gap through the permittivity change near the gap. Such a control of SPPs through the use of light could be boosted by the hybridized edge plasmon mode and a huge field enhancement using nanogap, gratings or metasurfaces, and could provide opportunities for ultrafast nano-plasmonic signal generation that is compatible with pervasive optical communication systems. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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13 pages, 3447 KiB

Open AccessArticle

Improvement in Hydriding and Dehydriding Features of Mg–TaF₅–VCl₃ Alloy by Adding Ni and x wt% MgH₂ (x = 1, 5, and 10) Together with TaF₅ and VCl₃

by Young-Jun Kwak and Myoung-Youp Song

Micromachines 2021, 12(10), 1194; https://doi.org/10.3390/mi12101194 - 30 Sep 2021

Cited by 2 | Viewed by 1188

Abstract

In our previous work, TaF₅ and VCl₃ were added to Mg, leading to the preparation of samples with good hydriding and dehydriding properties. In this work, Ni was added together with TaF₅ and VCl₃ to increase the reaction rates [...] Read more.

In our previous work, TaF₅ and VCl₃ were added to Mg, leading to the preparation of samples with good hydriding and dehydriding properties. In this work, Ni was added together with TaF₅ and VCl₃ to increase the reaction rates with hydrogen and the hydrogen-storage capacity of Mg. The addition of Ni together with TaF₅ and VCl₃ improved the hydriding and dehydriding properties of the TaF₅ and VCl₃-added Mg. MgH₂ was also added with Ni, TaF₅, and VCl₃ and Mg-x wt% MgH₂-1.25 wt% Ni-1.25 wt% TaF₅-1.25 wt% VCl₃ (x = 0, 1, 5, and 10) were prepared by reactive mechanical milling. The addition of MgH₂ decreased the particle size, lowered the temperature at which hydrogen begins to release rapidly, and increased the hydriding and dehydriding rates for the first 5 min. Adding 1 and 5 wt% MgH₂ increased the quantity of hydrogen absorbed for 60 min, H_a (60 min), and the quantity of hydrogen released for 60 min, H_d (60 min). The addition of MgH₂ improved the hydriding–dehydriding cycling performance. Among the samples, the sample with x = 5 had the highest hydriding and dehydriding rates for the first 5 min and the best cycling performance, with an effective hydrogen-storage capacity of 6.65 wt%. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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12 pages, 4570 KiB

Open AccessArticle

Macro-Modeling for N-Type Feedback Field-Effect Transistor for Circuit Simulation

by Jong Hyeok Oh and Yun Seop Yu

Micromachines 2021, 12(10), 1174; https://doi.org/10.3390/mi12101174 - 29 Sep 2021

Cited by 2 | Viewed by 1757

Abstract

In this study, we propose an improved macro-model of an N-type feedback field-effect transistor (NFBFET) and compare it with a previous macro-model for circuit simulation. The macro-model of the NFBFET is configured into two parts. One is a charge integrator circuit and the [...] Read more.

In this study, we propose an improved macro-model of an N-type feedback field-effect transistor (NFBFET) and compare it with a previous macro-model for circuit simulation. The macro-model of the NFBFET is configured into two parts. One is a charge integrator circuit and the other is a current generator circuit. The charge integrator circuit consisted of one N-type metal-oxide-semiconductor field-effect transistor (NMOSFET), one capacitor, and one resistor. This circuit implements the charging characteristics of NFBFET, which occur in the channel region. For the previous model, the current generator circuit consisted of one ideal switch and one resistor. The previous current generator circuit could implement I_DS-V_GS characteristics but could not accurately implement I_DS-V_DS characteristics. To solve this problem, we connected a physics-based diode model with an ideal switch in series to the current generator circuit. The parameters of the NMOSFET and diode used in this proposed model were fitted from TCAD data of the NFBFET, divided into two parts. The proposed model implements not only the I_DS-V_GS characteristics but also the I_DS-V_DS characteristics. A hybrid inverter and an integrate and fire (I&F) circuit for a spiking neural network, which consisted of NMOSFETs and an NFBFET, were simulated using the circuit simulator to verify a validation of the proposed NFBFET macro-model. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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10 pages, 5333 KiB

Open AccessArticle

Characterization of Nickel Oxide Nanoparticles Synthesized under Low Temperature

by Sung-Jei Hong, Hyuk-Jun Mun, Byeong-Jun Kim and Young-Sung Kim

Micromachines 2021, 12(10), 1168; https://doi.org/10.3390/mi12101168 - 28 Sep 2021

Cited by 29 | Viewed by 3975

Abstract

In this study, ultrafine nickel oxide nanoparticles (NiO NPs) were well synthesized using a simple wet chemical method under low temperature, 300 °C. An Ni(OH)₂ precursor was well precipitated by dropping NH₄OH into an Ni(Ac)₂ solution. TG-DTA showed that [...] Read more.

In this study, ultrafine nickel oxide nanoparticles (NiO NPs) were well synthesized using a simple wet chemical method under low temperature, 300 °C. An Ni(OH)₂ precursor was well precipitated by dropping NH₄OH into an Ni(Ac)₂ solution. TG-DTA showed that the weight of the precipitate decreases until 300 °C; therefore, the precursor was heat-treated at 300 °C. X-ray diffraction (XRD) patterns indicated that hexagonal-structured NiO NPs with (200) preferred orientation was synthesized. In addition, BET specific surface area (SSA) and HRTEM analyses revealed that spherical NiO NPs were formed with SSA and particle size of 60.14 m²/g and ca. 5–15 nm by using the low temperature method. FT-IR spectra of the NiO NPs showed only a sharp vibrating absorption peak at around 550 cm⁻¹ owing to the Ni-O bond. Additionally, in UV-vis absorption spectra, the wavelength for absorption edge and energy band gap of the ultrafine NiO NPs was 290 nm and 3.44 eV. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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10 pages, 2219 KiB

Open AccessArticle

Enhancement of Electrical Properties of Sol–Gel Indium–Tin–Oxide Films by Microwave Irradiation and Plasma Treatment

by Sung-Hun Kim and Won-Ju Cho

Micromachines 2021, 12(10), 1167; https://doi.org/10.3390/mi12101167 - 28 Sep 2021

Cited by 4 | Viewed by 2020

Abstract

We proposed the enhancement of the electrical properties of solution-processed indium–tin–oxide (ITO) thin films through microwave irradiation (MWI) and argon (Ar) gas plasma treatment. A cost- and time-effective heat treatment through MWI was applied as a post-deposition annealing (PDA) process to spin-coated ITO [...] Read more.

We proposed the enhancement of the electrical properties of solution-processed indium–tin–oxide (ITO) thin films through microwave irradiation (MWI) and argon (Ar) gas plasma treatment. A cost- and time-effective heat treatment through MWI was applied as a post-deposition annealing (PDA) process to spin-coated ITO thin films. Subsequently, the sheet resistance of MWI ITO thin films was evaluated before and after plasma treatment. The change in the sheet resistance demonstrated that MWI PDA and Ar plasma treatment significantly improved the electrical properties of the ITO thin films. Furthermore, X-ray photoelectron spectroscopy and X-ray diffraction analyses showed that the electrical properties of the ITO thin films were enhanced by the increase in oxygen vacancies due to the ion bombardment effect of high-energy plasma ions during Ar plasma treatment. Changes in the band gap structure of the ITO thin film due to the ion bombardment effect were also analyzed. The combination of MWI PDA and Ar plasma treatment presents new possibilities for improving the high-conductivity sol–gel ITO electrode. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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12 pages, 1981 KiB

Open AccessArticle

A Study on TiO₂ Surface Texturing Effect for the Enhancement of Photocatalytic Reaction in a Total Phosphorous Concentration Measurement System

by Jae Keon Kim, Seung Deok Kim, Jae Yong Lee, Chang Hee Kim, Hyeon-Su Lee, Seong Mo Koo, YoungJin Lee, Jong-Hoo Paik, Da Ye Kim and Seong Ho Kong

Micromachines 2021, 12(10), 1163; https://doi.org/10.3390/mi12101163 - 28 Sep 2021

Cited by 2 | Viewed by 1639

Abstract

Powerful sunlight, a high water temperature, and stagnation in the water flow induce eutrophication in rivers and lakes, which destroys the aquatic ecosystem and threatens the downstream water supply systems. Accordingly, it is very important to perform real-time measurements of nutrients that induce [...] Read more.

Powerful sunlight, a high water temperature, and stagnation in the water flow induce eutrophication in rivers and lakes, which destroys the aquatic ecosystem and threatens the downstream water supply systems. Accordingly, it is very important to perform real-time measurements of nutrients that induce algal growth, especially total phosphorus, to preserve and manage the aquatic ecosystem. To conduct quantitative analysis of the total phosphorus in the aquatic ecosystem, it is essential to perform a pretreatment process and quickly separate the phosphorus, combined with organic and inorganic materials, into a phosphate. In this study, the sandblasting process was used for the physical etching of the wafer, and photocatalytic materials were deposited on the surface with various roughness in order to improve the photocatalytic reaction surface and efficiency. The photocatalytic reaction was applied to combine the pretreated sample with the coloring agent for color development, and the absorbance of the colored sample was analyzed quantitatively to compare and evaluate the characteristics, followed by the surface increase in the photocatalytic materials. In addition, the pretreatment and measurement parts were materialized in a single chip to produce a small and light total phosphorus analysis sensor. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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11 pages, 5320 KiB

Open AccessArticle

Poly (Ethylene Glycol) Methyl Ether Methacrylate-Based Hydrogel and Cerium(IV) Oxide Nanoparticles as Ophthalmic Lens Material

by Min-Jae Lee, Seon-Young Park and A-Young Sung

Micromachines 2021, 12(9), 1111; https://doi.org/10.3390/mi12091111 - 16 Sep 2021

Cited by 3 | Viewed by 2295

Abstract

The functional hydrogel lens containing 2-hydroxyethylmethacrylate (HEMA) was manufactured by thermal polymerization. The physical properties of the produced hydrogel lens were measured and analyzed. In this study, HEMA, ethylene glycol dimethacrylate (EGDMA), and azobisisobutyronitrile (AIBN) were used for thermal copolymerization. Additionally, poly (ethylene [...] Read more.

The functional hydrogel lens containing 2-hydroxyethylmethacrylate (HEMA) was manufactured by thermal polymerization. The physical properties of the produced hydrogel lens were measured and analyzed. In this study, HEMA, ethylene glycol dimethacrylate (EGDMA), and azobisisobutyronitrile (AIBN) were used for thermal copolymerization. Additionally, poly (ethylene glycol) methyl ether methacrylate (PEGMEMA), 3-(Triethoxysilyl) propyl isocyanate (TEPI), and cerium(Ⅳ) oxide nanoparticles were used as additives to make a functional hydrogel lens. The mixture was heated at 100 °C for 90 min to produce the hydrogel ophthalmic lens by the cast mold method. The resulting physical properties showed that the water content and refractive index of the sample were in the ranges of 38.06~42.11% and 1.426~1.436, respectively. The addition of cerium oxide nanoparticles lowered the contact angle and allowed the hydrogel lens to block UV light. The tensile strength was also improved by 52.13% through cerium oxide nanoparticles, and up to 123.4% by using TEPI. Based on the results of this study, the produced ophthalmic lens is suitable for durable, UV-blocking high-performance lenses. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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11 pages, 27790 KiB

Open AccessArticle

Analysis of Shape Memory Behavior and Mechanical Properties of Shape Memory Polymer Composites Using Thermal Conductive Fillers

by Mijeong Kim, Seongeun Jang, Sungwoong Choi, Junghoon Yang, Jungpil Kim and Duyoung Choi

Micromachines 2021, 12(9), 1107; https://doi.org/10.3390/mi12091107 - 15 Sep 2021

Cited by 11 | Viewed by 2780

Abstract

Shape memory polymers (SMPs) are attracting attention for their use in wearable displays and biomedical materials due to their good biocompatibility and excellent moldability. SMPs also have the advantage of being lightweight with excellent shape recovery due to their low density. However, they [...] Read more.

Shape memory polymers (SMPs) are attracting attention for their use in wearable displays and biomedical materials due to their good biocompatibility and excellent moldability. SMPs also have the advantage of being lightweight with excellent shape recovery due to their low density. However, they have not yet been applied to a wide range of engineering fields because of their inferior physical properties as compared to those of shape memory alloys (SMAs). In this study, we attempt to find optimized shape memory polymer composites. We also investigate the shape memory performance and physical properties according to the filler type and amount of hardener. The shape memory composite was manufactured by adding nanocarbon materials of graphite and non-carbon additives of Cu. The shape-recovery mechanism was compared, according to the type and content of the filler. The shape fixation and recovery properties were analyzed, and the physical properties of the shape recovery composite were obtained through mechanical strength, thermal conductivity and differential scanning calorimetry analysis. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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13 pages, 2243 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Physiological and Behavioral Effects of SiO₂ Nanoparticle Ingestion on Daphnia magna

by Youngsam Kim, Afshin Samadi, Eun Heui Gwag, Jayoung Park, Minjeong Kwak, Jihoon Park, Tae Geol Lee and Young Jun Kim

Micromachines 2021, 12(9), 1105; https://doi.org/10.3390/mi12091105 - 14 Sep 2021

Cited by 11 | Viewed by 2588

Abstract

The increasingly widespread use of engineered nanoparticles in medical, industrial, and food applications has raised concerns regarding their potential toxicity to humans and the environment. Silicon dioxide nanoparticles (SiO₂ NPs), which have relatively low direct toxicity, have been increasingly applied in both [...] Read more.

The increasingly widespread use of engineered nanoparticles in medical, industrial, and food applications has raised concerns regarding their potential toxicity to humans and the environment. Silicon dioxide nanoparticles (SiO₂ NPs), which have relatively low direct toxicity, have been increasingly applied in both consumer products and biomedical applications, leading to significantly higher exposure for humans and the environment. We carried out a toxicity assessment of SiO₂ NPs using the common water flea D. magna by focusing on physiological and behavioral indicators such as heart rate, swimming performance, and growth. Exposure to SiO₂ NPs did not produce acute or chronic toxicity at limited concentrations (<100 μg/mL), but did have statistically significant negative effects on heart rate, swimming distance, and body size. The use of fluorescein isothiocyanate in a silica matrix allowed the tracing and visualization of clear SiO₂ NP accumulation in D. magna, which was confirmed by ICP-MS. Although exposure to SiO₂ NPs seemed to affect cardiac and swimming performance, such end-point experiments may be insufficient to fully understand the toxicity of these nanoparticles. However, the physiological and behavioral changes shown here suggest potential adverse effects on the aquatic environment by substances previously considered nontoxic. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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15 pages, 2830 KiB

Open AccessArticle

Differential Surface Capping Effects on the Applications of Simple Amino-Acid-Capped ZnS:Mn Nanoparticles

by Jinwoo Park and Cheong-Soo Hwang

Micromachines 2021, 12(9), 1064; https://doi.org/10.3390/mi12091064 - 31 Aug 2021

Cited by 2 | Viewed by 1701

Abstract

Water-dispersible ZnS:Mn nanoparticles (NPs) were prepared by capping their surface with simple structured amino acids: l-alanine (Ala), l-glycine (Gly), and l-valine (Val) molecules, which have very similar structures except for the terminal organic functional groups. The detailed characterization works for [...] Read more.

Water-dispersible ZnS:Mn nanoparticles (NPs) were prepared by capping their surface with simple structured amino acids: l-alanine (Ala), l-glycine (Gly), and l-valine (Val) molecules, which have very similar structures except for the terminal organic functional groups. The detailed characterization works for the prepared colloidal NPs were performed using various spectroscopic methods. In particular, the NPs commonly showed UV/visible absorption peaks around 325 nm and PL emission peaks around 590 nm, corresponding to the wavelength of orange color light. In this study, these amino-acid-capped NPs were applied as optical photosensors in the detection of specific divalent transition metal cations in the same conditions. Consequently, all three NPs showed exclusive fluorescence quenching effects upon the addition of Cu (II) metal ions, whereas their quenching efficiencies were quite different to each other. These experimental results indicated that the Gly-ZnS:Mn NPs (k = 4.09 × 10⁵ M⁻¹) can be the most effective optical photosensor for the detection of Cu²⁺ ions in water among the three NPs in the same conditions. This study showed that the steric effect of the capping ligand can be one of the key factors affecting the sensor activities of the ZnS:Mn NPs. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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11 pages, 23538 KiB

Open AccessArticle

PEI-Functionalized Carbon Nanotube Thin Film Sensor for CO₂ Gas Detection at Room Temperature

by Maeum Han, Soonyoung Jung, Yeonsu Lee, Daewoong Jung and Seong Ho Kong

Micromachines 2021, 12(9), 1053; https://doi.org/10.3390/mi12091053 - 30 Aug 2021

Cited by 17 | Viewed by 3594

Abstract

In this study, a polyethyleneimine (PEI)-functionalized carbon nanotube (CNT) sensor was fabricated for carbon dioxide detection at room temperature. Uniform CNT thin films prepared using a filtration method were used as resistive networks. PEI, which contains amino groups, can effectively react with CO [...] Read more.

In this study, a polyethyleneimine (PEI)-functionalized carbon nanotube (CNT) sensor was fabricated for carbon dioxide detection at room temperature. Uniform CNT thin films prepared using a filtration method were used as resistive networks. PEI, which contains amino groups, can effectively react with CO₂ gas by forming carbamates at room temperatures. The morphology of the sensor was observed, and the properties were analyzed by scanning electron microscope (SEM), Raman spectroscopy, and fourier transform infrared (FT-IR) spectroscopy. When exposed to CO₂ gas, the fabricated sensor exhibited better sensitivity than the pristine CNT sensor at room temperature. Both the repeatability and selectivity of the sensor were studied. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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11 pages, 3303 KiB

Open AccessArticle

Module-Type Triboelectric Nanogenerators Capable of Harvesting Power from a Variety of Mechanical Energy Sources

by Jaehee Shin, Sungho Ji, Jiyoung Yoon and Jinhyoung Park

Micromachines 2021, 12(9), 1043; https://doi.org/10.3390/mi12091043 - 29 Aug 2021

Cited by 7 | Viewed by 2764

Abstract

In this study, we propose a module-type triboelectric nanogenerator (TENG) capable of harvesting electricity from a variety of mechanical energy sources and generating power from diverse forms that fit the modular structure of the generator. The potential energy and kinetic energy of water [...] Read more.

In this study, we propose a module-type triboelectric nanogenerator (TENG) capable of harvesting electricity from a variety of mechanical energy sources and generating power from diverse forms that fit the modular structure of the generator. The potential energy and kinetic energy of water are used for the rotational motion of the generator module, and electricity is generated by the contact/separation generation mode between the two triboelectric surfaces inside the rotating TENG. Through the parametric design of the internal friction surface structure and mass ball, we optimized the output of the proposed structure. To magnify the power, experiments were conducted to optimize the electrical output of the series of the TENG units. Consequently, outputs of 250 V and 11 μA were obtained when the angle formed between the floor and the housing was set at 0° while nitrile was set as the positively charged material and the frequency was set at 7 Hz. The electrical signal generated by the module-type TENG can be used as a sensor to recognize the strength and direction of various physical quantities, such as wind and earthquake vibrations. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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13 pages, 4260 KiB

Open AccessArticle

Synthesis of Hyaluronic Acid-Conjugated Fe₃O₄@CeO₂ Composite Nanoparticles for a Target-Oriented Multifunctional Drug Delivery System

by Chang Ryong Lee, Gun Gyun Kim, Sung Bum Park and Sang Wook Kim

Micromachines 2021, 12(9), 1018; https://doi.org/10.3390/mi12091018 - 26 Aug 2021

Cited by 5 | Viewed by 2802

Abstract

This study is based on the principle that superparamagnetic iron oxide nanoparticles (Fe₃O₄) can be used to target a specific area given that their magnetic properties emerge when an external magnetic field is applied. Cerium oxide (CeO₂), [...] Read more.

This study is based on the principle that superparamagnetic iron oxide nanoparticles (Fe₃O₄) can be used to target a specific area given that their magnetic properties emerge when an external magnetic field is applied. Cerium oxide (CeO₂), which causes oxidative stress by generating reactive oxygen species (ROS) in the environment of tumor cells, was synthesized on the surface of superparamagnetic iron oxide nanoparticles to produce nanoparticles that selectively kill cancer cells. In addition, hyaluronic acid (HA) was coated on the cerium’s surface to target CD44-overexpressing tumor cells, and ^natZr was chelated on the Fe₃O₄@CeO₂ surface to show the usefulness of labeling the radioisotope ⁸⁹Zr (T1/2 = 3.3 d). The synthesis of Fe₃O₄@CeO₂ was confirmed by Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD) and Field Emission-Transmission Electron Microscope (FE-TEM). The coating of HA was confirmed by FT-IR, X-ray Photoelectron. Spectroscopy (XPS), FE-TEM, Energy-Dispersive X-ray Spectroscopy (EDS) and Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC). The sizes of the prepared nanoparticles were confirmed through FE-TEM and Field Emission-Scanning Electron (FE-SEM) (sizes of 15 to 30 nm), and it was confirmed that ^natZr was introduced onto the surface of the nanoparticles using EDS. The particle size of the dispersed material was limited through Dynamic Light Scattering (DLS) to about 148 nm in aqueous solution, which was suitable for the (enhanced permeation and retention) EPR effect. It was confirmed that the HA-coated nanoparticles have good dispersibility. Finally, a cytotoxicity evaluation confirmed the ability of CeO₂ to generate ROS and target the delivery of HA. In conclusion, Fe₃O₄@CeO₂ can effectively inhibit cancer cells through the activity of cerium oxide in the body when synthesized in nano-sized superparamagnetic coral iron that has magnetic properties. Subsequently, by labeling the radioactive isotope ⁸⁹Zr, it is possible to create a theranostic drug delivery system that can be used for cancer diagnosis. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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13 pages, 2669 KiB

Open AccessArticle

Evaluation of Crystalline Volume Fraction of Laser-Annealed Polysilicon Thin Films Using Raman Spectroscopy and Spectroscopic Ellipsometry

by Jeongsang Pyo, Bohae Lee and Han-Youl Ryu

Micromachines 2021, 12(8), 999; https://doi.org/10.3390/mi12080999 - 22 Aug 2021

Cited by 6 | Viewed by 3121

Abstract

We investigated the crystallinities of poly silicon (poly Si) annealed via green laser annealing (GLA) with a 532-nm pulsed laser and blue laser annealing (BLA) with 450-nm continuous-wave lasers. Three-dimensional heat transfer simulations were performed to obtain the temperature distributions in an amorphous [...] Read more.

We investigated the crystallinities of poly silicon (poly Si) annealed via green laser annealing (GLA) with a 532-nm pulsed laser and blue laser annealing (BLA) with 450-nm continuous-wave lasers. Three-dimensional heat transfer simulations were performed to obtain the temperature distributions in an amorphous silicon (a-Si) thin film, and GLA and BLA experiments were conducted based on the thermal simulation results. The crystallinity of annealed poly Si samples was analyzed using Raman spectroscopy and spectroscopic ellipsometry. To evaluate the degree of crystallization for the annealed samples quantitatively, the measured spectra of laser-annealed poly Si were fitted to those of crystalline Si and a-Si, and the crystal volume fraction (f_c) of the annealed poly Si sample was determined. Both the Raman spectroscopy and ellipsometry showed consistent results on f_c. The f_c values were found to reach >85% for optimum laser power of GLA and BLA, showing good crystallinity of the laser-annealed poly Si thin films comparable to thermal furnace annealing. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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10 pages, 12684 KiB

Open AccessArticle

Mechanical Durability of Flexible Printed Circuit Boards Containing Thin Coverlays Fabricated with Poly(Amide-Imide-Urethane)/Epoxy Interpenetrating Networks

by Jeongah Kim, Bo-Young Kim, Seong Dae Park, Ji-Hun Seo, Chan-Jae Lee, Myong Jae Yoo and Youngmin Kim

Micromachines 2021, 12(8), 943; https://doi.org/10.3390/mi12080943 - 10 Aug 2021

Cited by 3 | Viewed by 2311

Abstract

Because electronics are becoming flexible, the demand for techniques to manufacture thin flexible printed circuit boards (FPCBs) has increased. Conventional FPCBs are fabricated by attaching a coverlay film (41 μm) onto copper patterns/polyimide (PI) film to produce the structure of coverlay/Cu patterns/PI film. [...] Read more.

Because electronics are becoming flexible, the demand for techniques to manufacture thin flexible printed circuit boards (FPCBs) has increased. Conventional FPCBs are fabricated by attaching a coverlay film (41 μm) onto copper patterns/polyimide (PI) film to produce the structure of coverlay/Cu patterns/PI film. Given that the conventional coverlay consists of two layers of polyimide film and adhesive, its thickness must be reduced to generate thinner FPCBs. In this study, we fabricated 25-μm-thick poly(amide-imide-urethane)/epoxy interpenetrating networks (IPNs) to replace the thick conventional coverlay. Poly(amide-imide-urethane) (PAIU) was synthesized by reacting isocyanate-capped polyurethane with trimellitic anhydride and then mixed with epoxy resin to produce PAIU/epoxy IPNs after curing. Thanks to the soft segments of polyurethane, the elongation of PAIU/epoxy IPNs increased with increasing PAIU content and reached over 200%. After confirming the excellent thermal stability and chemical resistance of the PAIU/epoxy IPNs, we fabricated FPCBs by equipping them as coverlays. The mechanical durability of the FPCBs was evaluated through an MIT folding test, and the FPCB fabricated with PAIU/ep-2 was stable up to 164 folding cycles because of the balanced mechanical properties. Full article

(This article belongs to the Special Issue Nano Korea 2021)

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