14 results on '"Kim, Il‐Doo"'
Search Results
2. Imparting Metal Oxides with High Sensitivity Toward Light‐Activated NO2 Detection Via Tailored Interfacial Chemistry.
- Author
-
Park, Seyeon, Jeon, SungHyun, Kim, Honghui, Philips, James, Oh, DongHwan, Ahn, Jaewan, Kim, Minhyun, Park, Chungseong, Hong, Seungbum, Kim, Jihan, Jung, WooChul, and Kim, Il‐Doo
- Subjects
GAS detectors ,SURFACE chemistry ,CHEMICAL reactions ,METALLIC surfaces ,METAL activation ,LIGHT metals ,METALLIC oxides - Abstract
Activation of metal oxides by light is a robust yet facile approach to manipulating their surface chemistry for favorable reactions with target molecules in heterogeneous catalysis and gas sensors. However, a limited understanding of interface chemistry and the involved mechanism impedes the development of a rational design of oxide interfaces for light‐activated gas sensing. Herein, the TiOx‐assisted photosensitization of In2O3 toward NO2 sensing is investigated as a case study to elucidate the detailed mechanism of light‐activated surface chemistry at the metal/gas interface. The resultant heterogeneous oxides exhibit outstanding NO2 sensing performance under light irradiation thanks to abundant photoexcited electrons and holes that serve as adsorption and desorption sites, respectively, to accelerate both surface reactions. Furthermore, the facile transfer of electrons and holes across the TiOx‐In2O3 interface contributes to improving the reversibility of sensing kinetics. Through this study, the mechanistic understanding is established of how the surface chemistry of metal oxide surfaces can be tuned by light activation providing an effective route to the design fabrication of high‐performance gas sensors. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Overlaying Monolayer Metal–Organic Framework on PtSe2‐Based Gas Sensor for Tuning Selectivity.
- Author
-
Cho, Seong Rae, Kim, Dong‐Ha, Jeon, Mingyu, Rani, Pragya, Gyeon, Minseung, Kim, Yongman, Jo, Min‐kyung, Song, Seungwoo, Park, Jeong Young, Kim, Jihan, Kim, Il‐Doo, and Kang, Kibum
- Subjects
GAS detectors ,METAL-organic frameworks ,MOLECULAR dynamics ,DENSITY functional theory ,CRYSTAL surfaces ,MONOMOLECULAR films - Abstract
Transition metal dichalcogenides (TMDs) have attracted significant interest as gas‐sensing materials due to their unique crystal structure and surface. However, there are still issues when it comes to expanding the types of sensing gases for the TMD gas sensors. To extend gas‐sensing selectivity for the TMD gas sensors in this study, a monolayer (ML) 2D metal–organic framework (MOF) is introduced on top of the PtSe2 gas sensor, thereby tuning the major sensing analyte of PtSe2 from NO2 to H2S. Density functional theory calculations elucidate that the metal species of ML MOFs are attributed to the tuned selectivity of the analytes, based on the difference in binding energies. It is also demonstrated that ML MOF maintained the high responsivity of the pristine PtSe2 even at a low concentration of gas (200 ppb). This is further confirmed through the molecular dynamics simulations, which reveal that the ML feature of the ML MOF is highly essential to preserve the intrinsic ultra‐low limit detection properties of pristine PtSe2. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Low‐Thermal‐Budget Doping of 2D Materials in Ambient Air Exemplified by Synthesis of Boron‐Doped Reduced Graphene Oxide.
- Author
-
Cha, Jun‐Hwe, Kim, Dong‐Ha, Park, Cheolmin, Choi, Seon‐Jin, Jang, Ji‐Soo, Yang, Sang Yoon, Kim, Il‐Doo, and Choi, Sung‐Yool
- Subjects
GRAPHENE oxide ,X-ray photoelectron spectroscopy ,BORIC acid ,GRAPHENE synthesis ,MATERIALS - Abstract
Graphene oxide (GO) doping and reduction allow for physicochemical property modification to suit practical application needs. Herein, the challenge of simultaneous low‐thermal‐budget heteroatom doping of GO and its reduction in ambient air is addressed through the synthesis of B‐doped reduced GO (B@rGO) by flash irradiation of boric acid loaded onto a GO support with intense pulsed light (IPL). The effects of light power and number of shots on the in‐depth sequential doping and reduction mechanisms are investigated by ex situ X‐ray photoelectron spectroscopy and direct millisecond‐scale temperature measurements (temperature >1600 °C, < 10‐millisecond duration, ramping rate of 5.3 × 105 °C s−1). Single‐flash IPL allows the large‐scale synthesis of substantially doped B@rGO (≈3.60 at% B) to be realized with a thermal budget 106‐fold lower than that of conventional thermal methods, and the prepared material with abundant B active sites is employed for highly sensitive and selective room‐temperature NO2 sensing. Thus, this work showcases the great potential of optical annealing for millisecond‐scale ultrafast reduction and heteroatom doping of GO in ambient air, which allows the tuning of multiple physicochemical GO properties. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
5. Few‐Layered WS2 Nanoplates Confined in Co, N‐Doped Hollow Carbon Nanocages: Abundant WS2 Edges for Highly Sensitive Gas Sensors.
- Author
-
Koo, Won‐Tae, Cha, Jun‐Hwe, Jung, Ji‐Won, Choi, Seon‐Jin, Jang, Ji‐Soo, Kim, Dong‐Ha, and Kim, Il‐Doo
- Subjects
TUNGSTEN selenide ,DOPING agents (Chemistry) ,CARBON nanofibers ,GAS detectors ,CHEMICAL reactions - Abstract
Abstract: Edges of 2D transition metal dichalcogenides (TMDs) are well known as highly reactive sites, thus researchers have attempted to maximize the edge site density of 2D TMDs. In this work, metal‐organic framework (MOF) templates are introduced to synthesize few‐layered WS
2 nanoplates (a lateral dimension of ≈10 nm) confined in Co, N‐doped hollow carbon nanocages (WS2 _Co‐N‐HCNCs), for highly sensitive NO2 gas sensors. WS2 precursors are assembled in the surface cavity of Co‐based zeolite imidazole framework (ZIF‐67) and subsequent pyrolysis produced WS2 _Co‐N‐HCNCs. During the pyrolysis, the carbonized ZIF‐67 are doped by Co and N elements, and the growth of WS2 is effectively suppressed, creating few‐layered WS2 nanoplates functionalized Co‐N‐HCNCs. The WS2 _Co‐N‐HCNCs exhibit outstanding NO2 sensing characteristics at room temperature, in terms of response (48.2% to 5 ppm), selectivity, response and recovery speed, and detection limit (100 ppb). These results are attributed to the enhanced adsorption and desorption kinetics of NO2 on abundant WS2 edges, confined in the gas permeable HCNCs. This work opens up an efficient way for the facile synthesis of edge abundant few‐layered TMDs combined with porous carbon matrix via MOF templating route, for applications relying on highly active sites. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
6. Selective and sensitive detection of trimethylamine using ZnO–In2O3 composite nanofibers
- Author
-
Lee, Chul-Soon, Kim, Il-Doo, and Lee, Jong-Heun
- Subjects
- *
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]
- Published
- 2013
- Full Text
- View/download PDF
7. Advances and new directions in gas-sensing devices
- Author
-
Kim, Il-Doo, Rothschild, Avner, and Tuller, Harry L.
- Subjects
- *
GAS detectors , *HAZARDOUS substances , *DIAGNOSIS , *COSMETICS industry , *QUALITY control , *CHEMICAL industry - Abstract
Abstract: Gas sensors are employed in many applications including detection of toxic and combustible gases, monitoring emissions from vehicles and other combustion processes, breath analysis for medical diagnosis, and quality control in the chemicals, food and cosmetics industries. Many of these applications employ miniaturized solid-state devices, whose electrical properties change in response to the introduction of chemical analytes into the surrounding gas phase. Key challenges remain as to how to optimize sensor sensitivity, selectivity, speed of response and stability. The principles of operation of such devices vary and a brief review of operating principles based on potentiometric/amperometric, chemisorptive, redox, field effect and nanobalance approaches is presented. Due to simplicity of design and ability to stand up to harsh environments, metal oxide-based chemoresistive devices are commonly selected for these purposes and are therefore the focus of this review. While many studies have been published on the operation of such devices, an understanding of the underlying physicochemical principles behind their operation have trailed behind their technological development. In this article, a detailed review is provided which serves to update progress made along these lines. The introduction of nanodimensioned materials has had a particularly striking impact on the field over the past decade. Advances in materials processing has enabled the fabrication of tailored structures and morphologies offering, at times, orders of magnitude improvements in sensitivity, while high-resolution analytical methods have enabled a much improved examination of the structure and chemistry of these materials. Selected examples, illustrating the type of nanostructured devices being fabricated and tested, are discussed. This review concludes by highlighting trends suggesting directions for future progress. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
8. Macroporous TiO2 thin film gas sensors obtained using colloidal templates
- Author
-
Kim, Il-Doo, Rothschild, Avner, Yang, Dae-Jin, and Tuller, Harry L.
- Subjects
- *
THICK films , *SURFACE coatings , *SURFACES (Technology) , *THIN films - Abstract
Abstract: Chemical and physical synthesis routes were combined to prepare macroporous TiO2 thin films by RF sputtering onto poly methyl methacrylate (PMMA) microsphere templated substrates. The organic template was removed by thermal decomposition at 450°C leaving a thin layer of TiO2 anatase hollow hemispheres with diameter commensurate with that of the original PMMA microspheres (800nm). This unique morphology increased active surface area while reducing the deleterious interfacial effects between film and substrate leading to substantially enhanced NO2 sensitivity. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
9. Low‐Thermal‐Budget Doping: Low‐Thermal‐Budget Doping of 2D Materials in Ambient Air Exemplified by Synthesis of Boron‐Doped Reduced Graphene Oxide (Adv. Sci. 7/2020).
- Author
-
Cha, Jun‐Hwe, Kim, Dong‐Ha, Park, Cheolmin, Choi, Seon‐Jin, Jang, Ji‐Soo, Yang, Sang Yoon, Kim, Il‐Doo, and Choi, Sung‐Yool
- Subjects
GRAPHENE oxide ,GRAPHENE synthesis ,MATERIALS - Published
- 2020
- Full Text
- View/download PDF
10. 2D Oxide Sensors: Heterogeneous, Porous 2D Oxide Sheets via Rapid Galvanic Replacement: Toward Superior HCHO Sensing Application (Adv. Funct. Mater. 42/2019).
- Author
-
Jang, Ji‐Soo, Lee, Sang‐Eun, Choi, Seon‐Jin, Koo, Won‐Tae, Kim, Dong‐Ha, Shin, Hamin, Park, Hee Jung, and Kim, Il‐Doo
- Subjects
DETECTORS ,ELECTROLYTIC corrosion ,OXIDES - Abstract
2D Oxide Sensors: Heterogeneous, Porous 2D Oxide Sheets via Rapid Galvanic Replacement: Toward Superior HCHO Sensing Application (Adv. Funct. In article number 1903012, Hee Jung Park, Il-Doo Kim, and co-workers develop porous and heterogeneous SnO SB 2 sb /CoO SB I x i sb nanosheets by combining exfoliation with galvanic replacement reaction. Due to the high porosity, thin-thickness (<10 nm), and numerous heterogeneous junctions, the heterogeneous SnO SB 2 sb /CoO SB I x i sb nanosheets show super-sensitive HCHO sensing characteristics with a rapid response (<10 sec). [Extracted from the article]
- Published
- 2019
- Full Text
- View/download PDF
11. Heterogeneous, Porous 2D Oxide Sheets via Rapid Galvanic Replacement: Toward Superior HCHO Sensing Application.
- Author
-
Jang, Ji‐Soo, Lee, Sang‐Eun, Choi, Seon‐Jin, Koo, Won‐Tae, Kim, Dong‐Ha, Shin, Hamin, Park, Hee Jung, and Kim, Il‐Doo
- Subjects
METALLIC oxides ,SUBSTITUTION reactions ,POROUS metals ,OXIDES ,ELECTROLYTIC corrosion - Abstract
2D heterogeneous oxide nanosheets (NSs) have attracted much attention in various scientific fields owing to their exceptional physicochemical properties. However, the fabrication of 2D oxide NSs with abundant p–n interfaces and large amounts of mesopores is extremely challenging. Here, a facile synthesis of highly porous 2D heterogeneous oxide NSs (e.g., SnO2/CoOx) is suggested through a 2D oxide exfoliation approach combined with a fast galvanic replacement reaction (GRR). The ultrathin (<5 nm) layered CoOx NSs are simply prepared by ion‐exchange exfoliation and a subsequent GRR process that induces a rapid phase transition from p‐type CoOx to n‐type SnO2 metal oxides (<10 min). The controlled GRR process enables the creation of heterogeneous SnO2/CoOx NSs consisting of small SnO2 grain sizes (<10 nm), high porosity, numerous heterojunctions, and sub‐10 nm thickness, which are highly advantageous characteristics for chemiresistive sensors. Due to the advantage of these features, the porous SnO2/CoOx NSs exhibit an unparalleled HCHO‐sensing performance (Rair/Rgas > 35 @ 5 ppm with a response speed of 9.34 s) with exceptional selectivity compared to that of the state‐of‐the‐art metal oxide‐based HCHO gas sensors. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
12. Ultraselective and ultrasensitive detection of trimethylamine using MoO3 nanoplates prepared by ultrasonic spray pyrolysis.
- Author
-
Cho, Yoon Ho, Ko, You Na, Kang, Yun Chan, Kim, Il-Doo, and Lee, Jong-Heun
- Subjects
- *
TRIMETHYLAMINE , *MOLYBDENUM oxides , *ULTRASONICS , *PYROLYSIS , *STRUCTURAL plates , *HEAT treatment , *ELECTROCHEMICAL sensors - Abstract
Abstract: An ultraselective and ultrasensitive trimethylamine (TMA) sensor was achieved using MoO3 nanoplates-prepared by ultrasonic spray pyrolysis followed by a heat treatment at 450°C. The small and thin MoO3 nanoplates with gas-accessible structures showed an unusually high response to 5ppm TMA (ratio of resistance to air and gas=373.74) at 300°C with detection limit as low as 45ppb. Moreover, the ratios of the cross-responses to interfering gases (i.e., 5ppm C2H5OH, CO, CH4, C3H8, H2, and NO2) to the response to 5ppm TMA were extremely low (0.008–0.016). The source of the ultraselective and highly sensitive detection of TMA with negligible interference from other gases is discussed with respect to the acid/base properties, size, and morphology of the MoO3 sensing materials. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
13. Effect of metal/metal oxide catalysts on graphene fiber for improved NO2 sensing.
- Author
-
Eom, Wonsik, Jang, Ji-Soo, Lee, Sang Hoon, Lee, Eunsong, Jeong, Woojae, Kim, Il-Doo, Choi, Seon-Jin, and Han, Tae Hee
- Subjects
- *
ANNEALING of metals , *GRAPHENE oxide , *METAL catalysts , *GAS detectors , *PRECIOUS metals , *METALS at low temperatures , *METALLIC oxides - Abstract
• The non-noble metals are introduced on graphene-based fiber as a sensitizer for the high-performance chemiresistor. • Metal oxides on graphene fibers naturally are converted into metals at a relatively low temperature annealing (under 700 °C) due to catalytic effect of graphene. • The graphene fiber acts as a flexible conductive support as well as a catalyst for the deoxidation of metal oxide. • The metal/metal oxide/graphene fibers exhibited a 16 times higher response to NO 2 gas and recovery than metal oxide/graphene fiber without metal. • The proposed strategy opens a new avenue for the realization of high-performance devices, such as chemical catalysts, photoactive devices. [Display omitted] Noble metal/metal-oxide-based hybrid gas sensors exhibit a low operating temperature, remarkable sensitivity, and fast recovery. As additives, noble metals induce a catalytic sensitization effect, which promotes charge transfer from the metal oxide to the analyte molecules, the so-called spillover mechanism. This suggests that metal catalysts can improve gas sensing performance. Herein, for the first time, non-noble metals are introduced on hybrid metal oxide/graphene fibers as sensitizers to fabricate high-performance chemiresistive sensors. The formation of metal components can be effectively controlled by annealing the metal oxide on graphene. Remarkably, compared with the corresponding metal oxide/graphene fiber sensors without metal components, the metal/metal oxide/graphene fiber sensors exhibit over a 16-fold higher response to NO 2 gas as well as effective recovery characteristics. Specifically, the Cu/Cu 2 O/graphene and Ni/NiO/graphene fiber sensors operating at 150 °C exhibit sensitivities of 18.90 % and 0.82 %, respectively, for 5 ppm NO 2 gas. The proposed strategy to achieve flexible graphene fiber chemiresistors by decorating them with non-noble metal and metal oxide nanoparticles opens a new avenue for realizing high-performance devices, such as photovoltaic devices, photocatalysts, and chemical catalysts. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
14. Chemiresistive acetylene sensor fabricated from Ga-doped ZnO nanofibers functionalized with Pt catalysts.
- Author
-
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
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.