41 results on '"Kim, Il‐Doo"'
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2. Phase and microstructural evolution of Sn particles embedded in amorphous carbon nanofibers and their anode properties in Li-ion batteries
- Author
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Kim, Soohyun, Choi, Jin-Hoon, Lim, Dae-Soon, Lee, Jong-Heun, and Kim, Il-Doo
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- 2014
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3. Porous Nanofiber Membrane: Rational Platform for Highly Sensitive Thermochromic Sensor.
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Kim, Dong‐Ha, Bae, Jaehyeong, Lee, Jiyoung, Ahn, Jaewan, Hwang, Won‐Tae, Ko, Jaehyun, and Kim, Il‐Doo
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DISTRIBUTION (Probability theory) ,DETECTORS ,BODY temperature ,WEARABLE technology - Abstract
Thermochromic sensors provide an intuitive and real‐time solution for monitoring the local temperature with naked eyes. Conventional thermochromic sensors often utilize either solution‐type or dense film‐type platforms, which are suboptimal morphologies for exposing a large number of dye molecules to the surface, leading to low sensitivity and sluggish responding speeds. Herein, this article introduces rational synthetic routes to fabricate highly sensitive nanofiber (NF) sensor membranes loaded with thermochromic dyes (C3H6N6·CH2O)x‐loaded nanofibers (NFs) sensor membranes by alignment‐controllable electrospinning techniques (x–y perpendicular and rotary). The NF‐based porous sensor membranes exhibit two‐ to fivefold improved thermochromic sensitivity (ΔRGB) compared to those of dense film‐type sensors at 31.6–42.7 °C. This is attributed to the uniform distribution of dyes throughout the porous NF structure (≈95.7%), which exhibits excellent light transmittance that is 10–30‐fold higher than that of film‐type sensors. Based on the available shape‐conforming synthetic strategies, this article further demonstrates wearable thermochromic sensors in the forms of mask‐, patch‐, and bracelet‐type devices, which can accurately monitor body temperature in real time. [ABSTRACT FROM AUTHOR]
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- 2022
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4. Exhaled VOCs sensing properties of WO3 nanofibers functionalized by Pt and IrO2 nanoparticles for diagnosis of diabetes and halitosis
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Shin, Jungwoo, Choi, Seon-Jin, Youn, Doo-Young, and Kim, Il-Doo
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- 2012
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5. Electrospun SnO2 nanofiber mats with thermo-compression step for gas sensing applications
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Kim, Il-Doo, Jeon, Eun-Kyung, Choi, Seung-Hoon, Choi, Duck-Kyun, and Tuller, Harry L.
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- 2010
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6. Design of Hollow Nanofibrous Structures using Electrospinning: An Aspect of Chemical Sensor Applications.
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Cho, Hee‐Jin, Kim, Yoon Hwa, Park, Seyeon, and Kim, Il‐Doo
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ELECTROSPINNING ,METALLIC oxides ,CHEMICAL detectors ,SURFACE area - Abstract
Chemical gas sensors have attracted much attention with the purposes of environmental hazardous gas detection and health monitoring via exhaled breath analysis. In particular, semiconducting metal oxide (SMO)‐based chemiresistors have been considered as one of the most attractive sensing platforms owing to its simple operation, low cost, ease of miniaturization and integration to mobile devices. However, SMO‐based sensors suffer from sluggish gas reactions and poor responses. To enhance their sensing characteristics, one‐dimensional (1D) nanostructures with large surface area and high porosity are desired, since sensing reactions with analytes mainly occur at the surface of the sensing layers. In addition, uniform catalyst functionalization on SMO supports is beneficial in terms of gas response, reaction speed, and selectivity. In this review, we comprehensively highlight recent progresses on diverse hollow 1D nanofibrous structures prepared using a well‐reputed technique of electrospinning, and their unique morphological advantages as highly sensitive chemical sensing layers. Finally, future perspectives on the synthesis and sensing characterizations of hollow nanofibrous sensing materials functionalized with robust catalysts are discussed. [ABSTRACT FROM AUTHOR]
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- 2020
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7. Highly Conducting In2O3 Nanowire Network with Passivating ZrO2 Thin Film for Solution‐Processed Field Effect Transistors.
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Park, Hyungjin, Yoon, Ki Ro, Kim, Sung Kyu, Kim, Il‐Doo, Jin, Jungho, Kim, Yun Hyeok, and Bae, Byeong‐Soo
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NANOWIRES ,FIELD-effect transistors ,ELECTROSPINNING ,ZIRCONIUM oxide ,ELECTRONS ,SEMICONDUCTORS - Abstract
The article looks at study regarding solution processed in Nanowire field effect transistors (NWFETs) for conventional bottom gate top contacts (BGTC structure) with a multiple nanowire network. Topics discussed include utilization of electrospinning which produce a scalable continuous nanowire network, use of annealing process to remove the polymer matrix, bilayer structure comprising insulating zirconium oxide and electrons can pass through several insulating oxides and semiconducting buffer.
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- 2016
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8. Fe-N4 complex embedded free-standing carbon fabric catalysts for higher performance ORR both in alkaline & acidic media.
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Li, Bing, Sasikala, Suchithra Padmajan, Kim, Dong Ha, Bak, Junu, Kim, Il-Doo, Cho, EunAe, and Kim, Sang Ouk
- Abstract
Abstract Pt-based catalysts are suffering from the intrinsic high cost and poor stability for practical use in fuel cells. We develop a free-standing fabric type Pt-free high-performance oxygen reduction reaction (ORR) catalyst, consisting of N, Fe-codoped carbon nanofibers and graphene (N/Fe-CG) hybrids. Electrospinning is used to synthesize the free-standing fabric catalysts. Incorporation of graphene into the nanofiber structure greatly increases the electrical conductivity and catalytic surface area. X-ray photoelectron spectroscopy (XPS) analysis provides evidence that Fe-N 4 active centers are possibly formed in the catalyst, as is confirmed by electrochemical tests also. Compared to commercial Pt/C, our N/Fe-CG exhibits a similar level of catalytic activity but superior stability and methanol tolerance in both alkaline and acidic media, making it a good candidate for an ORR electrocatalyst in energy storage/conversion and other relevant applications. Graphical abstract fx1 Highlights • N, Fe-codoped free-standing carbon fabric ORR catalyst is successfully developed • The catalyst shows excellent catalytic properties in both alkaline and acidic media • Sample with N, Fe-codoping reveals better performance than single atom doped samples • FeN 4 complex formation is confirmed by electrochemical performance and XPS analysis [ABSTRACT FROM AUTHOR]
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- 2019
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9. Electrospun Nanostructures for High Performance Chemiresistive and Optical Sensors.
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Choi, Seon‐Jin, Persano, Luana, Camposeo, Andrea, Jang, Ji‐Soo, Koo, Won‐Tae, Kim, Sang‐Joon, Cho, Hee‐Jin, Kim, Il‐Doo, and Pisignano, Dario
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ELECTROSPINNING ,NANOSTRUCTURES ,OPTICAL sensors ,CHEMICAL detectors ,SURFACE morphology ,MICROSTRUCTURE - Abstract
Chemical sensors have been essential components in recent years due to the gathering attention in environmental monitoring and healthcare. In this review, the authors comprehensively highlight recent progresses on the 1D chemiresistive-type sensors based on semiconductor metal oxides (SMOs) and optical-type sensors, which are prepared by electrospinning technique. In the part of chemiresistive-type sensors, diverse synthesis techniques for 1D SMO nanofibrous structure are presented with controlled microstructure and surface morphology. In addition, unique functionalization routes of emerging nanocatalysts encapsulated by bio-inspired templates are described for the next generation catalyst on the 1D SMO nanofibers (NFs). For the optical-type sensors, new classes of 1D NFs employing specific absorption and emission properties are introduced. In particular, diverse 1D NF-based colorimetric and fluorescence sensors as well as Raman and surface-enhanced Raman scattering sensors are covered in the view point of material preparation and optical sensing properties. Finally, the authors prospect future research directions to overcome current limitations and challenges to achieve high performance chemical sensors. [ABSTRACT FROM AUTHOR]
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- 2017
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10. Facile synthesis and electrochemical properties of RuO2 nanofibers with ionically conducting hydrous layer
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Id Kim Il-Doo Kim, Hg Kim Ho-Gi Kim, Dy Youn Doo-Young Youn, Hl Tuller Harry L. Tuller, and Ts Hyun Tae-Seon Hyun
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Horizontal scan rate ,Materials science ,Nanotechnology ,General Chemistry ,engineering.material ,Electrochemistry ,Electrospinning ,Core (optical fiber) ,Coating ,Chemical engineering ,Nanofiber ,Materials Chemistry ,engineering ,Fiber ,Layer (electronics) - Abstract
The facile synthesis, by electrospinning of highly conductive RuO2 fiber mats as the conducting core of electrochemical capacitors, is reported. Electrospun RuO2 fiber mats, calcined at 400 °C, exhibited highly porous morphologies composed of crystalline RuO2 nano-particles with an average particle size of 10 nm. The highly conducting (σ = 288 S cm−1) fiber mats were used as the basis of a hybrid electrochemical capacitor in which the fiber mats served as the conducting core for electrochemically deposited hydrate RuO2·nH2O overlayers. These electrochemical capacitors exhibited superior characteristics: a high specific capacitance of ∼886.9 F g−1 (based on the mass of the hydrous RuO2 coating layer) at scan rate of 10 mV s−1 and high rate capability with a capacity loss of only 30% from 10 to 2000 mV s−1. This is attributed to the superior electron transport pathways provided by the fiber mat core to the upper ionically conducting hydrous RuO2 coating layer.
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- 2010
11. Amorphous Zinc Stannate (Zn2SnO4) Nanofibers Networks as Photoelectrodes for Organic Dye-Sensitized Solar Cells.
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Choi, Seung‐Hoon, Hwang, Daesub, Kim, Dong‐Young, Kervella, Yann, Maldivi, Pascale, Jang, Sung‐Yeon, Demadrille, Renaud, and Kim, Il‐Doo
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ZINC compounds ,AMORPHOUS substances ,PHOTOELECTRONS ,NANOFIBERS ,SOLAR cells ,MATERIALS science - Abstract
A new strategy for developing dye-sensitised solar cells (DSSCs) by combining thin porous zinc tin oxide (Zn
2 SnO4 ) fiber-based photoelectrodes with purely organic sensitizers is presented. The preparation of highly porous Zn2 SnO4 electrodes, which show high specific surface area up to 124 m2 /g using electrospinning techniques, is reported. The synthesis of a new organic donor-conjugate-acceptor (D-π-A) structured orange organic dye with molar extinction coefficient of 44 600 M−1 cm−1 is also presented. This dye and two other reference dyes, one organic and a ruthenium complex, are employed for the fabrication of Zn2 SnO4 fiber-based DSSCs. Remarkably, organic dye-sensitized DSSCs displayed significantly improved performance compared to the ruthenium complex sensitized DSSCs. The devices based on a 3 μm-thick Zn2 SnO4 electrode using the new sensitizer in conjunction with a liquid electrolyte show promising photovoltaic conversion up to 3.7% under standard AM 1.5G sunlight (100 mW cm−2 ). This result ranks among the highest reported for devices using ternary metal oxide electrodes. [ABSTRACT FROM AUTHOR]- Published
- 2013
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12. Thin-Wall Assembled SnO2 Fibers Functionalized by Catalytic Pt Nanoparticles and their Superior Exhaled-Breath-Sensing Properties for the Diagnosis of Diabetes.
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Shin, Jungwoo, Choi, Seon‐Jin, Lee, Inkun, Youn, Doo‐Young, Park, Chong Ook, Lee, Jong‐Heun, Tuller, Harry L., and Kim, Il‐Doo
- Abstract
Hierarchical SnO
2 fibers assembled from wrinkled thin tubes are synthesized by controlling the microphase separation between tin precursors and polymers, by varying flow rates during electrospinning and a subsequent heat treatment. The inner and outer SnO2 tubes have a number of elongated open pores ranging from 10 nm to 500 nm in length along the fiber direction, enabling fast transport of gas molecules to the entire thin-walled sensing layers. These features admit exhaled gases such as acetone and toluene, which are markers used for the diagnosis of diabetes and lung cancer. The open tubular structures facilitated the uniform coating of catalytic Pt nanoparticles onto the inner SnO2 layers. Highly porous SnO2 fibers synthesized at a high flow rate show five-fold higher acetone responses than densely packed SnO2 fibers synthesized at a low flow rate. Interestingly, thin-wall assembled SnO2 fibers functionalized by Pt particles exhibit a dramatically shortened gas response time compared to that of un-doped SnO2 fibers, even at low acetone concentrations. Moreover, Pt-decorated SnO2 fibers significantly enhance toluene response. These results demonstrate the novel and practical feasibility of thin-wall assembled metal oxide based breath sensors for the accurate diagnosis of diabetes and potential detection of lung cancer. [ABSTRACT FROM AUTHOR]- Published
- 2013
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13. Electronic sensitization of the response to C2H5OH of p-type NiO nanofibers by Fe doping.
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Yoon, Ji-Wook, Kim, Hyo-Joong, Kim, Il-Doo, and Lee, Jong-Heun
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P-type semiconductors ,NANOFIBERS ,SEMICONDUCTOR doping profiles ,ELECTROSPINNING ,MICROSTRUCTURE - Abstract
Pure and 0.18–13.2 at.% Fe-doped NiO nanofibers were prepared by electrospinning and their gas sensing characteristics and microstructural evolution were investigated. The responses ((R
g − Ra )/Ra , where Rg is the resistance in gas and Ra is the resistance in air) to 5 ppm C2 H5 OH, toluene, benzene, p-xylene, HCHO, CO, H2 , and NH3 at 350–500 ° C were significantly enhanced by Fe doping of the NiO nanofibers, while the responses of pure NiO nanofibers to all the analyte gases were very low ((Rg − Ra )/Ra = 0.07–0.78). In particular, the response to 100 ppm C2 H5 OH was enhanced up to 217.86 times by doping of NiO nanofibers with 3.04 at.% Fe. The variation in the gas response was closely dependent upon changes in the base resistance of the sensors in air. The enhanced gas response of Fe-doped NiO nanofibers was explained in relation to electronic sensitization, that is, the increase in the chemoresistive variation due to the decrease in the hole concentration induced by Fe doping. [ABSTRACT FROM AUTHOR]- Published
- 2013
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14. Selective and sensitive detection of trimethylamine using ZnO–In2O3 composite nanofibers
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Lee, Chul-Soon, Kim, Il-Doo, and Lee, Jong-Heun
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TRIMETHYLAMINE , *ZINC oxide , *INDIUM oxide , *METALLIC composites , *NANOFIBERS , *ELECTROSPINNING , *GAS detectors , *COMPARATIVE studies - Abstract
Abstract: Three different compositions of ZnO–In2O3 composite nanofibers were prepared by electrospinning, and their gas sensing characteristics were compared to those of pure ZnO and In2O3 nanofibers. All ZnO–In2O3 composite nanofibers showed high response to trimethylamine (TMA), relatively low cross-response to C2H5OH, and negligible cross-responses to CO and H2; pure ZnO or In2O3 nanofibers did not show selective detection of TMA. The maximum responses to 5ppm TMA of the ZnO–In2O3 composite nanofibers with the compositions of [Zn]:[In]=67:33, 50:50, and 33:67 by at% were 133.9 at 300°C, 82.9 at 350°C, and 119.4 at 375°C, respectively. Considering all the sensing characteristics such as gas response, selectivity, and sensing/recovering kinetics together, the operation of the ZnO–In2O3 nanofiber sensor with the composition of [Zn]:[In]=33:67 by at% at 375°C was determined to be in optimal condition to detect TMA. The significant enhancement of gas response and selectivity by the formation of composite nanofibers is discussed in relation to the variation of particle size, the formation of hetero-interfaces between ZnO and In2O3, and the combination of two sensing materials with different catalytic properties, gas adsorption behaviors, and acid–base properties. [Copyright &y& Elsevier]
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- 2013
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15. Facile Synthesis of p-type Perovskite SrTi0.65Fe0.35O3- δ Nanofibers Prepared by Electrospinning and Their Oxygen-Sensing Properties.
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Choi, Seung‐Hoon, Choi, Seon‐Jin, Min, Byoung Koun, Lee, Woon Young, Park, Jin Seong, and Kim, Il‐Doo
- Abstract
Quaternary p-type SrTi
0.65 Fe0.35 O3- δ (STFO) nanofibers with diameters ranging from 70 to 500 nm were synthesized via electrospinning and subsequent calcination at 750 °C. The STFO fibers showed single perovskite structure and polycrystalline fiber morphologies composed of small nanocrystallites in the range of 10-12 nm. The semiconducting oxygen sensor using STFO fiber network exhibited a wide temperature-independence of resistance (≈12 ± 4 kΩ) that exceeded the range of 600-950 °C, high oxygen response ( ${{R_{{\rm O}_{{\rm 2}} } } \mathord{\left/ {\vphantom {{R_{{\rm O}_{{\rm 2}} } } {R_{{\rm N}_{{\rm 2}} } }}} \right. \kern-\nulldelimiterspace} {R_{{\rm N}_{{\rm 2}} } }}$ = 4.08 at 20% O2 ), and a fast response time ( t = 2.1 s at 20% O2 ) upon cyclic oxygen exposure. These superior properties were attributed to the high surface-to-volume ratio of STFO fiber network and the effective diffusion of oxygen gas onto highly porous STFO-sensing layers. [ABSTRACT FROM AUTHOR]- Published
- 2013
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16. NO2 gas sensing properties of amorphous InGaZnO4 submicron-tubes prepared by polymeric fiber templating route
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Cho, Nam Gyu and Kim, Il-Doo
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NITROGEN dioxide , *GAS detectors , *AMORPHOUS substances , *INDIUM compounds , *FIBERS , *ELECTROSPINNING , *SURFACE coatings - Abstract
Abstract: One-dimensional (1D) amorphous InGaZnO4 (a-IGZO) submicron-tubes were synthesized in a method involving an electrospun polymeric fiber template and the direct RF-sputter-coating of a-IGZO films combined with subsequent calcination at 450°C. The a-IGZO hollow fibers with a diameter of 300nm and a shell thickness of 20–30nm showed an amorphous structure, as confirmed by XRD and HR-TEM analyses. Gas sensors using semiconducting a-IGZO tube networks exhibited n-type gas sensing characteristics and a 3.7-fold higher gas response (R gas /R air =109.5 at 2ppm NO2) compared to (R gas /R air =29.4) planar a-IGZO thin films at an operating temperature of 300°C. The enhanced gas response of a-IGZO tubes is attributed to the greater space charge modulation depth associated with the thin shell structures and the porous networks which are readily accessible by gas. [Copyright &y& Elsevier]
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- 2011
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17. Bi-functional RuO2–Co3O4 core–shell nanofibers as a multi-component one-dimensional water oxidation catalyst.
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Ko, Jong Wan, Ryu, Won-Hee, Kim, Il-Doo, and Park, Chan Beum
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OXIDATION of water ,ARTIFICIAL photosynthesis ,ELECTROSPINNING ,SOIL densification ,PHOTOSENSITIZERS - Abstract
The core–shell structure of RuO
2 –Co3 O4 fibers comprising the inner region of highly conductive RuO2 and the outer region of catalytic Co3 O4 provided a fast and effective transport pathway for holes to O2 -evolving sites, leading to a highly efficient water oxidation performance. [ABSTRACT FROM AUTHOR]- Published
- 2013
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18. Thin-walled NiO tubes functionalized with catalytic Pt for highly selective C2H5OH sensors using electrospun fibers as a sacrificial templateElectronic supplementary information (ESI) available. See DOI: 10.1039/c1cc13876f.
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Cho, Nam Gyu, Woo, Hyung-Sik, Lee, Jong-Heun, and Kim, Il-Doo
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TRANSITION metal oxides ,FUNCTIONAL groups ,NANOTUBES ,PLATINUM catalysts ,GLYCOLS ,BIOSENSORS ,ELECTROSPINNING ,FIBERS ,CHEMICAL templates ,SPUTTERING (Physics) - Abstract
Hollow thin walled NiO tubes functionalized by catalytic Pt were synthesized viananofiber templating and multilayered sputter-coating of Pt and NiO thin overlayers followed by heat-treatment at 600 °C. Sandwich Pt–NiO–Pt tube networks exhibited superior C2H5OH sensing response and remarkable selectivity against CO and H2gases. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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19. Microstructural control and selective C2H5OH sensing properties of Zn2SnO4nanofibers prepared by electrospinningElectronic supplementary information (ESI) available. See DOI: 10.1039/c1cc10707k.
- Author
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Choi, Seung-Hoon, Hwang, In-Sung, Lee, Jong-Heun, Oh, Seong-Geun, and Kim, Il-Doo
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MICROSTRUCTURE ,ETHANOL ,STANNIC oxide ,NANOFIBERS ,ELECTROSPINNING ,PHASE partition ,GAS detectors - Abstract
Microstructural evolution of spinel Zn2SnO4nanofibers was manipulated viaan in situphase separation process of inorganic precursors and a matrix polymer during electrospinning and calcination. Chemiresistive gas sensors using porous Zn2SnO4fibers exhibited superior C2H5OH sensing response. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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20. Macromol. Mater. Eng. 8/2017.
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Choi, Seon‐Jin, Persano, Luana, Camposeo, Andrea, Jang, Ji‐Soo, Koo, Won‐Tae, Kim, Sang‐Joon, Cho, Hee‐Jin, Kim, Il‐Doo, and Pisignano, Dario
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MACROMOLECULES ,ELECTROSPINNING ,PUBLISHING - Abstract
Front Cover: The feature describes two different types of chemical sensors, i.e., chemiresistive type sensors and optical sensors. For the chemiresistive type sensors, electrical signals are modulated during the reaction with chemical gas species. On the other hand, distinctive color changes are occurred in the case of optical sensors after the reaction with chemical analytes. The feature is designed for the review paper about one‐dimensional nanofibrous sensing structures for chemiresistive type sensors and optical sensors. This is reported by Seon‐Jin Choi, Luana Persano, Andrea Camposeo, Ji‐Soo Jang, Won‐Tae Koo, Sang‐Joon Kim, Hee‐Jin Cho, Il‐Doo Kim and Dario Pisignano, in article number 1600569. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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21. Advances in Electrospun Functional Nanofibers.
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Kim, Il‐Doo
- Published
- 2013
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22. An overview on electrospinning and its advancement toward hard and soft tissue engineering applications.
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Muthukrishnan, Lakshmipathy
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NANOFIBERS ,TISSUE engineering ,ELECTROSPINNING ,TECHNOLOGICAL innovations ,SMALL molecules ,NANOTECHNOLOGY - Abstract
One of the emerging technologies of the recent times harboring nanotechnology to fabricate nanofibers for various biomedical and environmental applications are electrospinning (nanofiber technology). Their relative ease in use, simplicity, functionality and diversity has surpassed the pitfalls encountered with the conventional method of generating fibers. This review aims to provide an overview of electrospinning, principle, methods, feed materials, and applications toward tissue engineering. To begin with, evolution of electrospinning and its typical apparatus have been briefed. Simultaneously, discussion on the production of nanofibers with diversified feed materials such as polymers, small molecules, colloids, and nanoparticles and its transformation into a powerful technology has been dealt with. Further, highlights on the application of nanofibers in tissue engineering and the commercialized products developed using nanofiber technology have been summed up. With this rapidly emerging technology, there would be a great demand pertaining to scalability and environmental challenge toward tissue engineering applications. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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23. Facile synthesis and electrochemical properties of conducting SrRuO3–RuO2 composite nanofibre mats
- Author
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Hyun, Tae-Seon, Kim, Ho-Gi, and Kim, Il-Doo
- Subjects
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NANOCOMPOSITE materials , *PEROVSKITE , *RUTHENIUM oxide superconductors , *ELECTROSPINNING , *STRONTIUM compounds , *ELECTROCHEMISTRY - Abstract
Abstract: This study reports the facile synthesis of highly conductive SrRuO3(SRO)–RuO2 composite nanofibre mats and their potential suitability for application in electrochemical capacitors as an active electrode material. SRO–RuO2/poly(vinyl acetate) composite nanofibre mats are electrospun on to a Au-coated SiO2/Si substrate and a Ti substrate, subsequently thermocompressed at 60°C, and calcined at various temperatures (from 350 to 850°C). The calcined SRO–RuO2 nanofibre mats exhibit porous morphologies and bundle shapes composed of multiple-fibrils with a nanoparticle diameter ranging from 20 to 50nm. Single SRO–RuO2 nanofibre and multiple SRO–RuO2 nanofibre mats show high electrical conductivity of 476 and 40.8Scm−1, respectively. Pseudocapacitors using SRO–RuO2 nanofibre mats calcined at 350°C exhibit a high specific capacitance of 192Fg−1 at a scan rate of 10mVs−1. The superior capacitance retention (83.4%) of the SRO–RuO2 nanofibre mats is maintained even at rapid scan rate of 1000mVs−1. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
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24. Controlled synthesis of electrospun hollow Pt-loaded SnO2 microbelts for acetone sensing.
- Author
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Bulemo, Peresi Majura, Kim, Dong-Ha, and Kim, Il-Doo
- Subjects
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ACETONE , *TIN oxides , *PLATINUM nanoparticles , *AIR resistance , *SCHOTTKY barrier , *METALLIC oxides , *HUMIDITY - Abstract
Electrospinning–etching strategy was employed to synthesize Pt-loaded SnO 2 hollow microbelts (Pt_SnO 2 HBLs) based chemiresistive-type sensor demonstrating high sensitivity and selectivity toward acetone gas. This strategy overcomes a major hurdle toward achieving ubiquitous gas diffusion in electrospun structures, and provides highly porous thin-walled HBLs with large surface area and small crystallites. [Display omitted] • In situ templating of SnO 2 with SiO 2 was employed to form Pt-loaded SiO 2 @SnO 2 core–shell microbelts. • Etching away of SiO 2 in the Pt-loaded SiO 2 @SnO 2 microbelts yielded Pt-loaded SnO 2 hollow microbelts. • The Pt-loaded SnO 2 hollow microbelts exhibited good response (R a /R g = 93.5) and selectivity toward 2 ppm acetone at 350 °C. Challenges for ubiquitous diffusion of gas analytes into semiconducting metal oxides (SMOs) based sensing layers have necessitated the introduction of unprecedented synthesis techniques for thin, porous and high-performance gas sensing materials. In this work, electrospinning and calcination were employed to prepare unprecedented SiO 2 –SnO 2 core–shell microbelts (hereinafter referred to as SiO 2 @SnO 2 BLs) followed by etching away of SiO 2 in NaOH solution (pH 12) to achieve hollow SnO 2 BLs (hereinafter referred to as SnO 2 HBLs) with mean crystal size of 14.01 nm, large BET surface area (143.5 m2‧g–1), high porosity (mean pore size of 5.7 nm), and shell thickness of 58.3 ± 11.4 nm. Sensitization of SnO 2 HBLs with apoferritin-templated platinum nanoparticles (Pt NPs) enhanced their detection capability toward acetone. Response (defined as R a /R g , where R a and R g are sensor resistances in air and target gas, respectively) of Pt(0.12 %)_SnO 2 HBLs toward 2 ppm acetone was up to 7.8 times higher compared to that of pristine SnO 2 HBLs, and exhibited faster response (9.2 s). The Pt(0.12 %)_SnO 2 HBLs based sensor indicated a promising long-term stability, and outstanding repeatability of response (R a /R g = 93.7 ± 0.89) toward 25 cycles of 2 ppm acetone exposure in a humid environment of 90 % relative humidity. This performance could be attributed to the unique morphology of HBLs, sensitization effects of catalytic Pt NPs, and enlargement of the electron-depleted layer resulting from a Schottky barrier between Pt NPs and SnO 2 grains. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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25. Generalized and feasible strategy to prepare ultra-porous, low density, compressible carbon nanoparticle sponges.
- Author
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Cheong, Jun Young, Benker, Lothar, Zhu, Jian, Youn, Doo-Young, Hou, Haoqing, Agarwal, Seema, Kim, Il-Doo, and Greiner, Andreas
- Subjects
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HEAT treatment , *NANOSTRUCTURED materials , *THERMAL conductivity , *CARBON , *LOW temperatures , *CARBON foams - Abstract
For the last two decades, nanostructured carbon materials have attracted significant attention, as they exhibit unusual physicochemical properties different from their bulk counterpart. Nevertheless, agglomeration and re-stacking of carbon nanostructures have always limited optimal performance, with larger loading amount. To solve this issue, porous and compressible carbon-based sponges have been researched, but most of the previously suggested carbon foams were either not very porous, synthesized at high temperature heat treatment, and/or not applicable for carbon nanoparticles. In this work, we have successfully fabricated ultra-porous (porosity about 98–99%), polyimide-carbon nanoparticle (PI–C) composites by combining Ketjen black nanoparticles with PI short fibers, by simple freeze-drying and subsequent heat treatments at low temperature (240 °C). Based on the analysis, it has been discovered that the fabricated PI-C sponges not only exhibit highly robust mechanical properties but also retain low thermal conductivity even in comparison with pristine PI sponges. This work provides a milestone in fabricating a number of C-electrospun polymeric sponges by freeze drying and subsequent heat treatments, which are expected to be utilized in various fields of research. Image 1 [ABSTRACT FROM AUTHOR]
- Published
- 2019
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26. Ag-coated one-dimensional orthorhombic Nb2O5 fibers as high performance electrodes for lithium storage.
- Author
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Cheong, Jun Young, Youn, Doo Young, Kim, Chanhoon, Jung, Ji-Won, Ogata, Alana F., Bae, Jin Gook, and Kim, Il-Doo
- Subjects
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ELECTRODES , *NIOBIUM , *LITHIUM-ion batteries , *ELECTRIC conductivity , *SILVER nanoparticles - Abstract
In the recent times, pseudocapacitive electrode materials have received great attention due to their considerable capability in storing ions at relatively fast charging rates. Among various candidates, niobium (V) pentoxide (Nb 2 O 5 ) has gained much attraction for lithium-ion batteries (LIBs) due to its insertion/extraction reaction with Li, safe redox potential, and considerably good capacity (about 200 mAhg −1 ). Nevertheless, low conductivity of Nb 2 O 5 has so far prevented its use as a viable electrode material for LIBs. In this study, we have successfully coated silver (Ag) nanoparticles (NPs) on the surface of one-dimensional orthorhombic Nb 2 O 5 fiber (1D T-Nb 2 O 5 ) using simple electrospinning processing. Ag NPs coated Nb 2 O 5 fibers (Ag-1D T-Nb 2 O 5 ) provided faster electron pathways, resulting in much improved capacity at a given current density with superior rate capabilities compared with pristine 1D T-Nb 2 O 5 . In addition, 1D T-Nb 2 O 5 was more suitable for coating Ag NPs compared with T-Nb 2 O 5 NPs, where its structural integrity was maintained even after cycling. As a result, effective coating of conductive Ag NPs on the 1D T-Nb 2 O 5 resulted in excellent cycle retention characteristics (179.7 mAhg −1 after 500 cycles at 500 mA g −1 ) as well as superior rate capabilities (103.6 mAhg −1 at a current density of 5000 mA g −1 ). [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
27. Facile and fast Na-ion intercalation employing amorphous black TiO2-x/C composite nanofiber anodes.
- Author
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Lee, Na-Won, Jung, Ji-Won, Lee, Jun-Seo, Jang, Hye-Yeon, Kim, Il-Doo, and Ryu, Won-Hee
- Subjects
- *
INTERCALATION reactions , *NANOFIBERS , *ENERGY storage , *TITANIUM dioxide , *SODIUM ions - Abstract
Structural and electronic modification of titanium oxide (TiO 2 ) nanomaterials induced by the co-introduction of fully disordered glass phase and oxygen vacancies can lead to remarkable advances in the electrode performance in emerging energy storage systems. We report on the effective co-creation of fully amorphous nanofibers (NFs) composed of black TiO 2-x and conductive carbons throughout the NF structure, and evaluate the materials as potential anodes in sodium-ion batteries. The black TiO 2-x nanofiber is successfully fabricated by electrospinning a precursor solution followed by a two-step sequential thermal treatment in an air and reducing atmosphere. The NF electrode could deliver approximately two-fold higher 2nd discharge capacity and an excellent kinetic performance even under high rates compared to that delivered by anatase-structured white TiO 2 NFs used as reference, because of (i) an inherent free volume in the glass phase corresponding to the enlarged Na + sites, (ii) increased electrical conductivity (low bandgap) resulting from the presence of Ti 3+ , (iii) introduction of conductive carbon agents around the TiO 2-x domain, and (iv) one-dimensional NF feature allowing numerous Na + reaction sites at the electrochemical interface. We also elucidate the morphological and structural changes in the nanofibers after discharge and charge by ex-situ characterizations. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
28. Porous SnO2-CuO nanotubes for highly reversible lithium storage.
- Author
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Cheong, Jun Young, Kim, Chanhoon, Jung, Ji-Won, Yoon, Ki Ro, and Kim, Il-Doo
- Subjects
- *
TIN oxides , *COPPER oxide , *NANOTUBES , *LITHIUM , *ELECTROSPINNING - Abstract
Facile synthesis of rationally designed structures is critical to realize a high performance electrode for lithium-ion batteries (LIBs). Among different candidates, tin(IV) oxide (SnO 2 ) is one of the most actively researched electrode materials due to its high theoretical capacity (1493 mAh g −1 ), abundance, inexpensive costs, and environmental friendliness. However, severe capacity decay from the volume expansion and low conductivity of SnO 2 have hampered its use as a feasible electrode for LIBs. Rationally designed SnO 2 -based nanostructures with conductive materials can be an ideal solution to resolve such limitations. In this work, we have successfully fabricated porous SnO 2 -CuO composite nanotubes (SnO 2 -CuO p-NTs) by electrospinning and subsequent calcination step. The porous nanotubular structure is expected to mitigate the volume expansion of SnO 2 , while the as-formed Cu from CuO upon lithiation allows faster electron transport by improving the low conductivity of SnO 2 . With a synergistic effect of both Sn and Cu-based oxides, SnO 2 -CuO p-NTs deliver stable cycling performance (91.3% of capacity retention, ∼538 mAh g −1 ) even after 350 cycles at a current density of 500 mA g −1 , along with enhanced rate capabilities compared with SnO 2 . [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
29. Mesoporous orthorhombic Nb2O5 nanofibers as pseudocapacitive electrodes with ultra-stable Li storage characteristics.
- Author
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Cheong, Jun Young, Jung, Ji-Won, Youn, Doo-Young, Kim, Chanhoon, Yu, Sunmoon, Cho, Su-Ho, Yoon, Ki Ro, and Kim, Il-Doo
- Subjects
- *
NANOFIBERS , *LITHIUM-ion batteries , *ORTHORHOMBIC crystal system , *MESOPOROUS materials , *ELECTROSPINNING - Abstract
Ultra-stable pseudocapacitive electrodes for lithium-ion batteries (LIBs) are increasing in demand as highly sustainable energy storage system with excellent charge transport is important. The establishment of facile, controllable, and scalable synthesis of pseudocapacitive electrode materials is an attractive solution to realize such objectives. Here, we have successfully fabricated mesoporous orthorhombic Nb 2 O 5 nanofibers (m-T-Nb 2 O 5 NFs) by simple single-spinneret electrospinning followed by calcination at 600 °C. As-formed m-T-Nb 2 O 5 NFs exhibit high surface area (23.7 m 2 g −1 ) and a number of mesopores in the vacant sites where organic polymer was once decomposed. Such rationally designed m-T-Nb 2 O 5 -NFs allow facile Li ion and electron transport, with pseudocapacitive behavior. Arising from the high surface area coupled with mesopores in-between the Nb 2 O 5 nanograins, it exhibits ultra-long cycle retention (a capacity of ∼160 mAh g −1 at 500 mA g −1 after 2000 cycles and ∼88 mAh g −1 at 3000 mA g −1 after 5000 cycles) and higher rate capability (∼70 mAh g −1 at 5000 mA g −1 ). Such cycle retention characteristics of m-T-Nb 2 O 5 -NFs are at least 100-fold slower capacity decay compared with previously reported one-dimensional (1D) Nb 2 O 5 nanostructures and even superior or comparable to recently reported Nb 2 O 5 -graphene composite materials. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
30. Facile synthetic method of catalyst-loaded ZnO nanofibers composite sensor arrays using bio-inspired protein cages for pattern recognition of exhaled breath.
- Author
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Cho, Hee-Jin, Kim, Sang-Joon, Choi, Seon-Jin, Jang, Ji-Soo, and Kim, Il-Doo
- Subjects
- *
NANOPARTICLE synthesis , *CHEMICAL detectors , *ZINC oxide , *NANOFIBERS , *COMPOSITE materials , *PATTERN recognition systems , *METAL oxide semiconductors , *CATALYSTS - Abstract
Functionalization of catalytic nanoparticles (NPs) on semiconductor metal oxide (SMO) sensing layer is an indispensable process to obtain improved sensitivity and selectivity for high performance chemical sensors. It is a critical challenge to achieve homogeneous distribution of nanoscale catalysts on SMO in consideration that gas sensing characteristics of SMO-based sensing layer are significantly influenced by the size and distribution of catalysts. Here, we propose a highly effective functionalization method to achieve well-distributed catalytic NPs onto one dimensional (1D) SMO nanofibers (NFs) using protein cage templates: apoferrtin. By simply replacing precursor in the apoferritin assisted method, not only precious catalyst such as Pt but also non-precious catalysts such as La and Cu were successfully synthesized in nanoscale ( i.e. , 3–5 nm). Furthermore, the apoferritin-encapsulated catalysts exhibited high dispersion property due to repulsive force between protein shells. For this reason, catalytic NPs were homogeneously decorated on ZnO NFs after electrospinning followed by calcination. Catalytic Pt NPs and Cu NPs functionalized ZnO NFs exhibited approximately 6.38-fold (R air /R gas = 13.07) and 2.95-fold (R air /R gas = 6.04) improved acetone response compared with the response (R air /R gas = 2.05) of pristine ZnO NFs. In the case of La NPs functionalized ZnO NFs, 9.31-fold improved nitrogen monoxide response (R air /R gas = 10.06) was achieved compared with the response of pristine ZnO NFs. The four catalyst-ZnO composite NFs successfully distinguished simulated breath components such as acetone, toluene, nitrogen monoxide, carbon monoxide, and ammonia with well-classified patterns by principal component analysis (PCA). This work demonstrated a robustness of synthetic and functionalization method using bio-inspired protein templates combined with electrospinning technique and a promising potential of using non-precious catalysts to establish diverse sensing material libraries that can be applicable to breath pattern recognition for diagnosis of diseases. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
31. WO3 nanofibers functionalized by protein-templated RuO2 nanoparticles as highly sensitive exhaled breath gas sensing layers.
- Author
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Kim, Kwang-Hun, Kim, Sang-Joon, Cho, Hee-Jin, Kim, Nam-Hoon, Jang, Ji-Soo, Choi, Seon-Jin, and Kim, Il-Doo
- Subjects
- *
TUNGSTEN oxides , *NANOFIBERS , *APOFERRITIN , *CHEMICAL templates , *RUTHENIUM oxides , *METAL nanoparticles , *GAS detectors - Abstract
In this work, a novel catalytic synthesis and functionalization method using apoferritin is used to fabricate RuO 2 nanoparticles (NPs) loaded WO 3 nanofibers (NFs) for potential diagnosis of diabetes. Catalytic ruthenium (Ru) NPs with very small average diameters of 1.8 ± 0.9 nm were synthesized using apoferritin which is a hollow protein cage, and were easily functionalized on WO 3 NFs by introducing electrospinning solution with W precursor and polyvinylpyrrolidone (PVP). As-spun Ru NPs-loaded W precursor/PVP composite NFs were calcined at 600 °C for 1 h in air atmosphere to achieve RuO 2 -functionalized WO 3 NFs. The small size and uniform distribution of catalytic RuO 2 NPs were well maintained due to hollow nature of apoferritin cages after calcination. The chemo-resistive sensors using RuO 2 -functionalized WO 3 NFs showed significantly enhanced acetone (CH 3 COCH 3 ) sensing response (R air /R gas = 78.61–5 ppm), which was 7.4 times higher than the response (R air /R gas = 10.61–5 ppm) of pristine WO 3 NFs at highly humid atmosphere (95% RH). In addition, the RuO 2 -functionalized WO 3 NFs showed outstanding selectivity toward acetone gas in comparison with other gases such as hydrogen sulfide (H 2 S), toluene (C 6 H 5 CH 3 ), ethanol (C 2 H 5 OH), pentane (C 5 H 12 ), ammonia (NH 3 ), hydrogen (H 2 ), and water vapor (H 2 O) at 5 ppm. These results represent potential feasibility for the detection of acetone in exhaled breath for diagnosis of diabetes. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
32. Highly sensitive and selective acetone sensing performance of WO3 nanofibers functionalized by Rh2O3 nanoparticles.
- Author
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Kim, Nam-Hoon, Choi, Seon-Jin, Kim, Sang-Joon, Cho, Hee-Jin, Jang, Ji-Soo, Koo, Won-Tae, Kim, Moonil, and Kim, Il-Doo
- Subjects
- *
ACETONE , *NANOPARTICLES , *NANOFIBERS , *X-ray diffraction , *ELECTROSPINNING - Abstract
In this work, catalytic Rh 2 O 3 -functionalized WO 3 nanofibers (NFs) were synthesized via an electrospinning route and used as a highly selective acetone-sensing layer for potential diagnosis of diabetes. Catalytic rhodium nanoparticles (Rh NPs) with average diameters of 5.0 ± 0.52 nm, which were synthesized by the polyol process, were dispersed in water with W precursor and poly(vinylpyrrolidone) (PVP) for electrospinning. As-spun Rh NP-loaded W precursor/PVP composite NFs were calcined at 600 °C for 1 h in air atmosphere to achieve Rh 2 O 3 -decorated WO 3 NFs. Microstructure evolution and chemical composition of Rh 2 O 3 -decorated WO 3 NFs as a function of Rh-loading amounts, i.e., 0.01 wt%, 0.05 wt%, 0.10 wt%, and 0.15 wt%, were examined using energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The mean size (30 nm) of the WO 3 crystallites in Rh 2 O 3 -decorated WO 3 NFs was much smaller than that (60 nm) of the WO 3 crystallites in pristine WO 3 NFs. The Rh 2 O 3 -decorated WO 3 NFs showed outstanding acetone (CH 3 COCH 3 ) sensing response ( R air / R gas = 41.2 to 5 ppm), which was 4.6 times higher than the response ( R air / R gas = 9.0 to 5 ppm) of pristine WO 3 NFs at highly humid atmosphere (95% RH). In addition, superior acetone cross-sensitivity of the Rh 2 O 3 -decorated WO 3 NFs was observed in other interfering gases such as pentane ( n -C 5 H 12 ), ammonia (NH 3 ), toluene (C 6 H 5 CH 3 ), carbon monoxide (CO), and ethanol (C 2 H 5 OH) at 5 ppm. These results are highly promising for the accurate and selective detection of acetone in exhaled breath for potential diagnosis of diabetes. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
33. Highly sensitive and selective hydrogen sulfide and toluene sensors using Pd functionalized WO3 nanofibers for potential diagnosis of halitosis and lung cancer.
- Author
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Kim, Nam-Hoon, Choi, Seon-Jin, Yang, Dae-Jin, Bae, Jihyun, Park, Jongjin, and Kim, Il-Doo
- Subjects
- *
HYDROGEN sulfide , *TOLUENE , *DETECTORS , *TUNGSTEN oxides , *NANOFIBERS , *LUNG cancer , *BAD breath , *PALLADIUM catalysts - Abstract
In this work, we report a remarkably improved toluene response and superior cross-sensitivity against H2S molecules by combining Pd catalysts and highly porous WO3 nanofibers (NFs). We functionalized Pd catalysts inside and/or outside of WO3 NFs synthesized by electrospinning, which is a facile and versatile process for producing webs of metal oxide NFs. Pd-embedded WO3 NFs were obtained by the electrospinning of a Pd and W composite precursor/poly(methyl methacrylate) (PMMA) solution followed by calcination at 700°C. Pd nanoparticles (NPs) (6–10nm) synthesized by a polyol method were decorated on the WO3 NFs (Pd-NPs/WO3 NFs) by the attachment of the Pd NPs on as-prepared WO3 NFs. The gas sensing characteristics of pure WO3, Pd-embedded WO3, Pd-NPs/WO3, and Pd-NPs/Pd-embedded WO3 NFs were tested using H2S and toluene gases in a highly humid atmosphere (RH 90%), which is similar to human exhaled breath. The results showed that the Pd-NPs/Pd-embedded WO3 NFs whose inner and outer layers were decorated by Pd catalysts, exhibited a high toluene response (R air/R gas =5.5 at 1ppm) and remarkable selectivity against H2S (R air/R gas =1.36 at 1ppm) at 350°C, whereas pristine WO3 NFs showed superior H2S response (R air/R gas =11.1 at 1ppm) along with a negligible response toward toluene (R air/R gas =1.27 at 1ppm). The highly porous WO3 NFs decorated with Pd catalysts, exhibited potential feasibility, i.e., a low limit of detection (LOD) of 20ppb (R air/R gas =1.32) at 350°C, for application in VOCs sensors, particularly for diagnoses of lung cancer. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
34. Synthesis of an Al2O3-coated polyimide nanofiber mat and its electrochemical characteristics as a separator for lithium ion batteries.
- Author
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Lee, Juneun, Lee, Cho-Long, Park, Kyusung, and Kim, Il-Doo
- Subjects
- *
LITHIUM-ion batteries , *ALUMINUM oxide synthesis , *POLYIMIDES , *SURFACE coatings , *NANOFIBERS , *WETTING , *AMIC acids - Abstract
Abstract: Polyimide (PI) nanofibers with an average diameter of 300 nm, possessing superior electrolyte wettability and thermal stability, are synthesized by electrospinning a poly(amic acid) (PAA) solution followed by an imidization process. The large pore volume of the PI nanofiber mat can facilitate faster Li+-ion transport and greater rate capability, but it also cause an irreversible increase in cell impedance during long term cycling. To overcome these problems, thin Al2O3 over-layers are coated on both sides of a PI separator via a dip-coating process. The Al2O3-coated PI separators exhibit enhanced capacity, cyclability (95.53% retention after 200 cycles at 1 C), and rate capabilities (78.91% at 10 C) compared to the bare PI separator (68.65% at 10 C) and a commercial polypropylene separator (18.25% at 10 C) with a limited increase of cell impedance. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
35. Selectivity enhancement of SnO2 nanofiber gas sensors by functionalization with Pt nanocatalysts and manipulation of the operation temperature.
- Author
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Jang, Bong-Hoon, Landau, Osnat, Choi, Seon-Jin, Shin, Jungwoo, Rothschild, Avner, and Kim, Il-Doo
- Subjects
- *
STANNIC oxide , *GAS detectors , *NANOSTRUCTURED materials synthesis , *NANOFIBERS , *PLATINUM catalysts , *TEMPERATURE effect , *ELECTROSPINNING , *CALCINATION (Heat treatment) - Abstract
We report on facile synthesis of SnO2 nanofibers (NFs) functionalized by Pt nanoparticles (NPs) with various loading contents (0.05–0.4wt%) and their gas response toward H2, NO2, NH3, CO, and SO2 gases as a function of the operation temperature (100–450°C) and gas concentration (0.125–2.5ppm). Mesoporous SnO2 NFs with large surface-to-volume ratio, which facilitates sensitive gas response, were synthesized by electrospinning followed by subsequent calcination at 500°C for 2h. Colloidal Pt NPs synthesized by simple polyol method were immobilized on SnO2 NFs as a catalytic sensitizer to H2 oxidation. The gas sensing properties and response kinetics were significantly affected by the Pt NPs and the operation temperature. It was found that 0.1wt% Pt-loaded SnO2 sensor showed the highest H2 response (I gas/I air =16.6 at 2.5ppm) at 300°C. A remarkably high NO2 response (I air/I gas =57.0 at 2.5ppm) was achieved in the case of pristine SnO2 sensor at 150°C. This work demonstrates that sensitive and selective detection of H2 and NO2 gases with negligible cross-response to interfering gases such as NH3, CO, and SO2 can be obtained by decoration with Pt NPs on metal oxide NFs in conjunction with manipulation of the operation temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
36. Highly sensitive SnO2 hollow nanofiber-based NO2 gas sensors
- Author
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Cho, Nam Gyu, Yang, Dae Jin, Jin, Mi-Jin, Kim, Ho-Gi, Tuller, Harry L., and Kim, Il-Doo
- Subjects
- *
STANNIC oxide , *NANOFIBERS , *NITROGEN dioxide , *GAS detectors , *ELECTROSPINNING , *RADIO frequency , *SPUTTERING (Physics) , *THIN films - Abstract
Abstract: SnO2 hollow nanofibers (HNFs) with diameters of 300–500nm were fabricated via electrospinning of templating nanofibers and RF-sputtering of SnO2 thin overlayers (15–20nm thick and comparable grain size) followed by heat-treatment at 450°C. Gas sensors using these HNFs exhibited n-type gas sensing characteristics and an enhanced gas response to 2ppm NO2 (R gas /R air =81.4) as compared to that (R gas /R air =19.9) of planar SnO2 thin films. The enhanced response to NO2 is attributed to the greater accessible active area and the greater space charge modulation depth associated with the hollow thin walled structures. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
37. Pd-doped TiO2 nanofiber networks for gas sensor applications
- Author
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Moon, Jaehyun, Park, Jin-Ah, Lee, Su-Jae, Zyung, Taehyoung, and Kim, Il-Doo
- Subjects
- *
NANOFIBERS , *GAS detectors , *TEMPERATURE effect , *ELECTROSPINNING , *METALLIC oxides , *PALLADIUM - Abstract
Abstract: This work presents a new route to enhance the sensitivity of nanocrystalline TiO2 fibers based gas sensors. Pure and Pd-doped TiO2 nanofiber mats were synthesized by electrospinning and subsequent calcination. Highly porous fibrillar morphology was observed in the resultant nanocrystalline TiO2 fibers. In addition to anatase TiO2 crystallites, tiny (∼2nm) PdO crystallites were observed in the Pd-doped TiO2 fibers. The sensors using Pd-doped TiO2 fibers showed promising gas sensing characteristics, such as low operation temperature (180°C) and sufficient gas response (R/R o =38 to 2.1ppm NO2). The techniques outlined here offer new means for preparing novel metal-oxide nanofibers with catalytic dopants. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
38. Chemiresistive acetylene sensor fabricated from Ga-doped ZnO nanofibers functionalized with Pt catalysts.
- Author
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Park, Seyeon, Bulemo, Peresi Majura, Koo, Won-Tae, Ko, Jaehyun, and Kim, Il-Doo
- Subjects
- *
METALLIC oxides , *NANOFIBERS , *GAS detectors , *POROUS metals , *METAL nanoparticles , *METALLIC composites , *ZINC oxide - Abstract
• Porosity control of nanofibers: The high porosity of the metal oxide nanofibers is the key to achieving the dual sensitization owing to their high gas permeability and numerous active sites. Both saponin and water-ethanol co-solvent play critical roles in modifying morphology of nanofibers into elliptical nanofibers during electrospinning. Additionally, saponin forms numerous pores in the nanofibers when being burnt out during calcination. These porous, elliptical nanofibers possess a larger surface area and porosity.Saponin and water-ethanol co-solvent enabled porous, elliptical nanofibers to emerge. • Bifunctional Ga doping: Ga dopants enhanced sensing performance via conductivity improvement and grain growth inhibition. • Functionalization of Pt catalysts : Spill-over effects and chemical sensitization of remarkably improved C 2 H 2 sensitivity. Herein, we demonstrate a sensitization strategy via solid-solution doping and catalytic metal nanoparticles (NPs) onto porous metal oxide nanofibers (NFs) for superior acetylene (C 2 H 2) sensing capabilities. The introduction of dopants and catalysts not only increases the inherent reactivity of metal oxides, but also induces the spillover of C 2 H 2 onto metal oxides, significantly improving the sensing properties. We elucidate that the high porosity of the metal oxide NFs, prepared by electrospinning and utilizing saponin as a sacrificial template, is the key to achieving high gas permeability and numerous active sites. Consequently, Ga-doped ZnO porous NFs functionalized with Pt catalysts exhibited the highest C 2 H 2 sensing responses among the current state-of-the-art C 2 H 2 sensors (R a /R g = 26.2 at 400 °C) with a fast response time (10.2 s), at a particularly low concentration of 5 ppm. Moreover, these NFs showed excellent selectivity against the interfering gas (H 2 , C 7 H 8 , CO, CH 4 , C 8 H 10 , CH 3 COCH 3 , HCHO and C 2 H 5 OH) and outstanding stability up to 20 sensing cycles to 0.4 ppm of C 2 H 2. These results provide an efficient strategy to tailor composites of metal oxide nanostructures, dopants, and catalysts for highly sensitive gas sensors. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
39. Cross-aligned carbon nanofibrous network for efficient and outstanding high-rate Li storage capability.
- Author
-
Cheong, Jun Young, Hwang, Wontae, Lee, Jiyoung, and Kim, Il-Doo
- Subjects
- *
CARBON composites , *CARBON nanofibers , *ELECTRIC batteries , *COMPOSITE materials , *HEAT treatment , *CHEMICAL kinetics , *CARBON - Abstract
• Synthesis of CA-CNF by insulating block electrospinning & carbonization. • Formation of cross-aligned network even after heat treatment. • Faster reaction kinetics and regular electron pathway of CA-CNF. • High-rate cyclability of CA-CNF (259.4 mAh g−1 at 3000 mA g−1). The conventional use of metallic current collector in an electrochemical cell results in decreased loading of active materials and hence limited capacity in consideration of all the inactive current collector components. In response to this trend, a number of conductive, free-standing materials have been proposed as electrodes, which would act as both current collector and active materials. Here, in this study, we have firstly developed the cross-aligned carbon nanofiber (CA-CNF) for efficient Li storage, especially at high current densities. Using the insulating block electrospinning, the nanofibers can be aligned in a certain direction, where it is viable to fabricate cross-aligned nanofibers in a cost-effective and scalable manner. Attributed to faster kinetics and regular electron pathway arising from CA-CNF, it exhibits an excellent high-rate cyclability (259.4 mAh g−1 at a current density of 3000 mA g−1). This work builds up a milestone in suggesting a cross-aligned carbon nanofibrous network as efficient Li storage, which can also be applied to various electrode materials embedded cross-aligned conductive composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
40. Electrospun fibers based on carbohydrate gum polymers and their multifaceted applications.
- Author
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Padil, Vinod V.T, Cheong, Jun Young, KP, AkshayKumar, Makvandi, Pooyan, Zare, Ehsan Nazarzadeh, Torres-Mendieta, Rafael, Wacławek, Stanisław, Černík, Miroslav, Kim, Il-Doo, and Varma, Rajender S.
- Subjects
- *
POLYMERS , *CARBOHYDRATES , *FIBERS , *MASS production , *GUMS & resins , *GUAR gum - Abstract
• Electrospinning of plant- and microbial-based carbohydrate gums is discussed. • Electrospinning parameters with respect to gums are illustrated. • Applications of carbohydrate gum-derived electrospun fibers are exemplified. Electrospinning has garnered significant attention in view of its many advantages such as feasibility for various polymers, scalability required for mass production, and ease of processing. Extensive studies have been devoted to the use of electrospinning to fabricate various electrospun nanofibers derived from carbohydrate gum polymers in combination with synthetic polymers and/or additives of inorganic or organic materials with gums. In view of the versatility and the widespread choice of precursors that can be deployed for electrospinning, various gums from both, the plants and microbial-based gum carbohydrates are holistically and/or partially included in the electrospinning solution for the preparation of functional composite nanofibers. Moreover, our strategy encompasses a combination of natural gums with other polymers/inorganic or nanoparticles to ensue distinct properties. This early established milestone in functional carbohydrate gum polymer-based composite nanofibers may be deployed by specialized researchers in the field of nanoscience and technology, and especially for exploiting electrospinning of natural gums composites for diverse applications. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
41. Electrospun Nanostructures for High Performance Chemiresistive and Optical Sensors
- Author
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Dario Pisignano, Luana Persano, Sang-Joon Kim, Seon-Jin Choi, Andrea Camposeo, Hee-Jin Cho, Ji-Soo Jang, Won-Tae Koo, Il-Doo Kim, Choi, Seon Jin, Persano, Luana, Camposeo, Andrea, Jang, Ji Soo, Koo, Won Tae, Kim, Sang Joon, Cho, Hee Jin, Kim, Il Doo, and Pisignano, Dario
- Subjects
Materials science ,Nanostructure ,Polymers and Plastics ,General Chemical Engineering ,Nanofibers ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,symbols.namesake ,Chemiresistive sensor ,Materials Chemistry ,Electrospinning ,business.industry ,Organic Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Template ,Semiconductor ,Nanofiber ,Chemical sensors ,Optical sensors ,symbols ,Surface modification ,0210 nano-technology ,Raman spectroscopy ,business ,Raman scattering - Abstract
Chemical sensors have been essential components in recent years due to the gathering attention in environmental monitoring and healthcare. In this review, the authors comprehensively highlight recent progresses on the 1D chemiresistive-type sensors based on semiconductor metal oxides (SMOs) and optical-type sensors, which are prepared by electrospinning technique. In the part of chemiresistive-type sensors, diverse synthesis techniques for 1D SMO nanofibrous structure are presented with controlled microstructure and surface morphology. In addition, unique functionalization routes of emerging nanocatalysts encapsulated by bio-inspired templates are described for the next generation catalyst on the 1D SMO nanofibers (NFs). For the optical-type sensors, new classes of 1D NFs employing specific absorption and emission properties are introduced. In particular, diverse 1D NF-based colorimetric and fluorescence sensors as well as Raman and surface-enhanced Raman scattering sensors are covered in the view point of material preparation and optical sensing properties. Finally, the authors prospect future research directions to overcome current limitations and challenges to achieve high performance chemical sensors.
- Published
- 2017
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