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Do DP, Hong C, Bui VQ, Pham TH, Seo S, Do VD, Phan TL, Tran KM, Haldar S, Ahn B, Lim SC, Yu WJ, Kim S, Kim J, Lee H. Highly Efficient Van Der Waals Heterojunction on Graphdiyne toward the High-Performance Photodetector. Adv Sci (Weinh) 2023; 10:e2300925. [PMID: 37424035 PMCID: PMC10477878 DOI: 10.1002/advs.202300925] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 06/04/2023] [Indexed: 07/11/2023]
Abstract
Graphdiyne (GDY), a new 2D material, has recently proven excellent performance in photodetector applications due to its direct bandgap and high mobility. Different from the zero-gap of graphene, these preeminent properties made GDY emerge as a rising star for solving the bottleneck of graphene-based inefficient heterojunction. Herein, a highly effective graphdiyne/molybdenum (GDY/MoS2 ) type-II heterojunction in a charge separation is reported toward a high-performance photodetector. Characterized by robust electron repulsion of alkyne-rich skeleton, the GDY based junction facilitates the effective electron-hole pairs separation and transfer. This results in significant suppression of Auger recombination up to six times at the GDY/MoS2 interface compared with the pristine materials owing to an ultrafast hot hole transfer from MoS2 to GDY. GDY/MoS2 device demonstrates notable photovoltaic behavior with a short-circuit current of -1.3 × 10-5 A and a large open-circuit voltage of 0.23 V under visible irradiation. As a positive-charge-attracting magnet, under illumination, alkyne-rich framework induces positive photogating effect on the neighboring MoS2 , further enhancing photocurrent. Consequently, the device exhibits broadband detection (453-1064 nm) with a maximum responsivity of 78.5 A W-1 and a high speed of 50 µs. Results open up a new promising strategy using GDY toward effective junction for future optoelectronic applications.
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Affiliation(s)
- Dinh Phuc Do
- Department of ChemistrySungkyunkwan UniversitySuwon16419Republic of Korea
| | - Chengyun Hong
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Viet Q Bui
- Advanced Institute of Science and TechnologyThe University of Danang41 Le DuanDanang92026Vietnam
| | - Thi Hue Pham
- Advanced Institute of Science and TechnologyThe University of Danang41 Le DuanDanang92026Vietnam
| | - Sohyeon Seo
- Department of ChemistrySungkyunkwan UniversitySuwon16419Republic of Korea
- Creative Research InstituteSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Van Dam Do
- Department of Electrical and Computer EngineeringSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Thanh Luan Phan
- Department of Electrical and Computer EngineeringSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Kim My Tran
- Department of ChemistrySungkyunkwan UniversitySuwon16419Republic of Korea
| | - Surajit Haldar
- Department of ChemistrySungkyunkwan UniversitySuwon16419Republic of Korea
| | - Byung‐wook Ahn
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Seong Chu Lim
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer EngineeringSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Seong‐Gon Kim
- Department of Physics and Astronomy and Center for Computational SciencesMississippi State UniversityMississippi StateMS39762USA
| | - Ji‐Hee Kim
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Hyoyoung Lee
- Department of ChemistrySungkyunkwan UniversitySuwon16419Republic of Korea
- Creative Research InstituteSungkyunkwan UniversitySuwon16419Republic of Korea
- Department of BiophysicsSungkyunkwan UniversitySuwon16419Republic of Korea
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2
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Manh DH, Thanh TD, Phan TL, Yang DS. Towards hard-magnetic behavior of CoFe 2O 4 nanoparticles: a detailed study of crystalline and electronic structures, and magnetic properties. RSC Adv 2023; 13:8163-8172. [PMID: 36922942 PMCID: PMC10009764 DOI: 10.1039/d3ra00525a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/05/2023] [Indexed: 03/18/2023] Open
Abstract
We have used the coprecipitation and mechanical-milling methods to fabricate CoFe2O4 nanoparticles with an average crystallite size (d) varying from 81 to ∼12 nm when changing the milling time (t m) up to 180 min. X-ray diffraction and Raman-scattering studies have proved the samples crystalizing in the spinel structure. Both the lattice constant and residual strain tend to increase when t m(d) increases (decreases). The analysis of magnetization data has revealed a change in the coercivity (H c) towards the hard-magnetic properties. Specifically, the maximum H c is about 2.2 kOe when t m = 10 min corresponding to d ≈ 29 nm; beyond this t m(d) value, H c gradually decreases. Meanwhile, the increase of t m always reduces the saturation magnetization (M s) from ∼69 emu g-1 for t m = 0 to 35 emu g-1 for t m = 180 min. The results collected as analyzing X-ray absorption data have indicated a mixed valence state of Fe2+,3+ and Co2+ ions. We think that the migration and redistribution of these cations between the tetrahedral and octahedral sites together with lattice distortions and defects induced by the milling process have impacted the magnetic properties of the CoFe2O4 nanoparticles.
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Affiliation(s)
- D H Manh
- Institute of Materials Science, Vietnam Academy of Science and Technology 18 Hoang Quoc Viet Hanoi Viet Nam
| | - T D Thanh
- Institute of Materials Science, Vietnam Academy of Science and Technology 18 Hoang Quoc Viet Hanoi Viet Nam
| | - T L Phan
- Department of Physics, Hankuk University of Foreign Studies Yongin 449-791 South Korea.,Faculty of Engineering Physics and Nanotechnology, VNU-University of Engineering and Technology 144 Xuan Thuy, Cau Giay Ha Noi Viet Nam
| | - D S Yang
- Department of Science Education, Chungbuk National University Cheongju 360-763 South Korea
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Vu VT, Phan TL, Vu TTH, Park MH, Do VD, Bui VQ, Kim K, Lee YH, Yu WJ. Synthesis of a Selectively Nb-Doped WS 2-MoS 2 Lateral Heterostructure for a High-Detectivity PN Photodiode. ACS Nano 2022; 16:12073-12082. [PMID: 35913119 DOI: 10.1021/acsnano.2c02242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In this study, selective Nb doping (P-type) at the WS2 layer in a WS2-MoS2 lateral heterostructure via a chemical vapor deposition (CVD) method using a solution-phase precursor containing W, Mo, and Nb atoms is proposed. The different chemical activity reactivity (MoO3 > WO3 > Nb2O5) enable the separation of the growth temperature of intrinsic MoS2 to 700 °C (first grown inner layer) and Nb-doped WS2 to 800 °C (second grown outer layer). By controlling the Nb/(W+Nb) molar ratio in the solution precursor, the hole carrier density in the p-type WS2 layer is selectively controlled from approximately 1.87 × 107/cm2 at 1.5 at.% Nb to approximately 1.16 × 1013/cm2 at 8.1 at.% Nb, while the electron carrier density in n-type MoS2 shows negligible change with variation of the Nb molar ratio. As a result, the electrical behavior of the WS2-MoS2 heterostructure transforms from the N-N junction (0 at.% Nb) to the P-N junction (4.5 at.% Nb) and the P-N tunnel junction (8.1 at.% Nb). The band-to-band tunneling at the P-N tunnel junction (8.1 at.% Nb) is eliminated by applying negative gate bias, resulting in a maximum rectification ratio (105) and a minimum channel resistance (108 Ω). With this optimized photodiode (8.1 at.% Nb at Vg = -30 V), an Iphoto/Idark ratio of 6000 and a detectivity of 1.1 × 1014 Jones are achieved, which are approximately 20 and 3 times higher, respectively, than the previously reported highest values for CVD-grown transition-metal dichalcogenide P-N junctions.
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Affiliation(s)
- Van Tu Vu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thi Thanh Huong Vu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Mi Hyang Park
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Van Dam Do
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Viet Quoc Bui
- Department of Chemistry, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kunnyun Kim
- Korea Electronics Technology Institute, Seongnam, 13509, Republic of Korea
| | - Young Hee Lee
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
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Phan TL, Seo S, Cho Y, An Vu Q, Lee YH, Duong DL, Lee H, Yu WJ. CNT-molecule-CNT (1D-0D-1D) van der Waals integration ferroelectric memory with 1-nm 2 junction area. Nat Commun 2022; 13:4556. [PMID: 35961959 PMCID: PMC9374722 DOI: 10.1038/s41467-022-32173-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 07/19/2022] [Indexed: 11/20/2022] Open
Abstract
The device’s integration of molecular electronics is limited regarding the large-scale fabrication of gap electrodes on a molecular scale. The van der Waals integration (vdWI) of a vertically aligned molecular layer (0D) with 2D or 3D electrodes indicates the possibility of device’s integration; however, the active junction area of 0D-2D and 0D-3D vdWIs remains at a microscale size. Here, we introduce the robust fabrication of a vertical 1D-0D-1D vdWI device with the ultra-small junction area of 1 nm2 achieved by cross-stacking top carbon nanotubes (CNTs) on molecularly assembled bottom CNTs. 1D-0D-1D vdWI memories are demonstrated through ferroelectric switching of azobenzene molecules owing to the cis-trans transformation combined with the permanent dipole moment of the end-tail -CF3 group. In this work, our 1D-0D-1D vdWI memory exhibits a retention performance above 2000 s, over 300 cycles with an on/off ratio of approximately 105 and record current density (3.4 × 108 A/cm2), which is 100 times higher than previous study through the smallest junction area achieved in a vdWI. The simple stacking of aligned CNTs (4 × 4) allows integration of memory arrays (16 junctions) with high device operational yield (100%), offering integration guidelines for future molecular electronics. The van der Waals integration of molecular layer (0D) with 2D or 3D electrodes is limited at microscale junction. Here, the authors introduce 1D-0D-1D vdWI memory with 1 nm2 junction achieved by cross-stacking t-CNT on molecularly assembled b-CNT.
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Affiliation(s)
- Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Sohyeon Seo
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Yunhee Cho
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419, Republic of Korea.,Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
| | - Quoc An Vu
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.,Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.,Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea. .,Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
| | - Hyoyoung Lee
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419, Republic of Korea. .,Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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Vu VT, Vu TTH, Phan TL, Kang WT, Kim YR, Tran MD, Nguyen HTT, Lee YH, Yu WJ. One-Step Synthesis of NbSe 2/Nb-Doped-WSe 2 Metal/Doped-Semiconductor van der Waals Heterostructures for Doping Controlled Ohmic Contact. ACS Nano 2021; 15:13031-13040. [PMID: 34350752 DOI: 10.1021/acsnano.1c02038] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
van der Waals heterostructures (vdWHs) of metallic (m-) and semiconducting (s-) transition-metal dichalcogenides (TMDs) exhibit an ideal metal/semiconductor (M/S) contact in a field-effect transistor. However, in the current two-step chemical vapor deposition process, the synthesis of m-TMD on pregrown s-TMD contaminates the van der Waals (vdW) interface and hinders the doping of s-TMD. Here, NbSe2/Nb-doped-WSe2 metal-doped-semiconductor (M/d-S) vdWHs are created via a one-step synthesis approach using a niobium molar ratio-controlled solution-phase precursor. The one-step growth approach synthesizes Nb-doped WSe2 with a controllable doping concentration and metal/doped-semiconductor vdWHs. The hole carrier concentration can be precisely controlled by controlling the Nb/(W + Nb) molar ratio in the precursor solution from ∼3 × 1011/cm2 at Nb-0% to ∼1.38 × 1012/cm2 at Nb-60%; correspondingly, the contact resistance RC value decreases from 10 888.78 at Nb-0% to 70.60 kΩ.μm at Nb-60%. The Schottky barrier height measurement in the Arrhenius plots of ln(Isat/T2) versus q/KBT demonstrated an ohmic contact in the NbSe2/WxNb1-xSe2 vdWHs. Combining p-doping in WSe2 and M/d-S vdWHs, the mobility (27.24 cm2 V-1 s-1) and on/off ratio (2.2 × 107) are increased 1238 and 4400 times, respectively, compared to that using the Cr/pure-WSe2 contact (0.022 cm2 V-1 s-1 and 5 × 103, respectively). Together, the RC value using the NbSe2 contact shows 2.46 kΩ.μm, which is ∼29 times lower than that of using a metal contact. This method is expected to guide the synthesis of various M/d-S vdWHs and applications in future high-performance integrated circuits.
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Affiliation(s)
- Van Tu Vu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thi Thanh Huong Vu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Won Tae Kang
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Young Rae Kim
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Minh Dao Tran
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Huong Thi Thanh Nguyen
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
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Kang WT, Phan TL, Ahn KJ, Lee I, Kim YR, Won UY, Kim JE, Lee YH, Yu WJ. Selective Pattern Growth of Atomically Thin MoSe 2 Films via a Surface-Mediated Liquid-Phase Promoter. ACS Appl Mater Interfaces 2021; 13:18056-18064. [PMID: 33827208 DOI: 10.1021/acsami.1c04005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) offer numerous advantages over silicon-based application in terms of atomically thin geometry, excellent opto-electrical properties, layer-number dependence, band gap variability, and lack of dangling bonds. The production of high-quality and large-scale TMD films is required with consideration of practical technology. However, the performance of scalable devices is affected by problems such as contamination and patterning arising from device processing; this is followed by an etching step, which normally damages the TMD film. Herein, we report the direct growth of MoSe2 films on selective pattern areas via a surface-mediated liquid-phase promoter using a solution-based approach. Our growth process utilizes the promoter on the selective pattern area by enhancing wettability, resulting in a highly uniform MoSe2 film. Moreover, our approach can produce other TMD films such as WSe2 films as well as control various pattern shapes, sizes, and large-scale areas, thus improving their applicability in various devices in the future. Our patterned MoSe2 field-effect transistor device exhibits a p-type dominant conduction behavior with a high on/off current ratio of ∼106. Thus, our study provides general guidance for direct selective pattern growth via a solution-based approach and the future design of integrated devices for a large-scale application.
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Affiliation(s)
- Won Tae Kang
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kyung Jin Ahn
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ilmin Lee
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Young Rae Kim
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ui Yeon Won
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ji Eun Kim
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
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7
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Fox GJ, Nguyen VN, Dinh NS, Nghiem LPH, Le TNA, Nguyen TA, Nguyen BH, Nguyen HD, Tran NB, Nguyen TL, Le TN, Nguyen VH, Phan TL, Nguyen KC, Ho J, Pham DC, Britton WJ, Bestrashniy JRBM, Marks GB. Post-treatment Mortality Among Patients With Tuberculosis: A Prospective Cohort Study of 10 964 Patients in Vietnam. Clin Infect Dis 2020; 68:1359-1366. [PMID: 30202910 DOI: 10.1093/cid/ciy665] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 08/14/2018] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Tuberculosis is the leading infectious cause of death. Steep reductions in tuberculosis-related mortality are required to realize the World Health Organization's "End Tuberculosis Strategy." However, accurate mortality estimates are lacking in many countries, particularly following discharge from care. This study aimed to establish the mortality rate among patients with pulmonary tuberculosis in Vietnam and to quantify the excess mortality in this population. METHODS We conducted a prospective cohort study among adult patients treated for smear-positive pulmonary tuberculosis in 70 clinics across Vietnam. People living in the same households were recruited as controls. Participants were re-interviewed and their survival was established at least 2 years after their treatment with an 8-month standardized regimen. The presence of relapse was established by linking identifying data on patients and controls to clinic registries. Verbal autopsies were performed. The cumulative mortality among patients was compared to that among a control population, adjusting for age and gender. RESULTS We enrolled 10964 patients and 25707 household controls. Among enrolled tuberculosis patients, 9% of patients died within a median follow-up period of 2.9 years: 342 (3.1%) during treatment and 637 (5.8%) after discharge. The standardized mortality ratio was 4.0 (95% confidence interval 3.7-4.2) among patients with tuberculosis, compared to the control population. Tuberculosis was the likely cause of death for 44.7% of these deceased patients. CONCLUSIONS Patients treated for tuberculosis had a markedly elevated risk of death, particularly in the post-treatment period. Interventions to reduce tuberculosis mortality must enhance the early detection of drug-resistance, improve treatment effectiveness, and address non-communicable diseases.
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Affiliation(s)
- G J Fox
- Faculty of Medicine and Health, University of Sydney, Australia.,Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - V N Nguyen
- National Lung Hospital, Ba Dinh, Hanoi, Vietnam
| | - N S Dinh
- National Lung Hospital, Ba Dinh, Hanoi, Vietnam
| | - L P H Nghiem
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - T N A Le
- National Lung Hospital, Ba Dinh, Hanoi, Vietnam
| | - T A Nguyen
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - B H Nguyen
- National Lung Hospital, Ba Dinh, Hanoi, Vietnam.,Centre for Operational Research, International Union Against Tuberculosis and Lung Disease, Paris, France
| | - H D Nguyen
- Pham Ngoc Thach Hospital, Ho Chi Minh City, Vietnam
| | - N B Tran
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - T L Nguyen
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - T N Le
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - V H Nguyen
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - T L Phan
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - K C Nguyen
- National Lung Hospital, Ba Dinh, Hanoi, Vietnam.,Hanoi Medical University, Hanoi, Vietnam
| | - J Ho
- Faculty of Medicine and Health, University of Sydney, Australia
| | - D C Pham
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
| | - W J Britton
- Faculty of Medicine and Health, University of Sydney, Australia.,Centenary Institute of Cancer Medicine and Cell Biology, University of Sydney, Camperdown, New South Wales, Australia
| | | | - G B Marks
- Woolcock Institute of Medical Research, Glebe, New South Wales, Australia.,South Western Sydney Clinical School, University of New South Wales, Kensington, New South Wales, Australia
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Yun SJ, Duong DL, Ha DM, Singh K, Phan TL, Choi W, Kim Y, Lee YH. Ferromagnetic Order at Room Temperature in Monolayer WSe 2 Semiconductor via Vanadium Dopant. Adv Sci (Weinh) 2020; 7:1903076. [PMID: 32382479 PMCID: PMC7201245 DOI: 10.1002/advs.201903076] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/07/2020] [Accepted: 02/27/2020] [Indexed: 05/22/2023]
Abstract
Diluted magnetic semiconductors including Mn-doped GaAs are attractive for gate-controlled spintronics but Curie transition at room temperature with long-range ferromagnetic order is still debatable to date. Here, the room-temperature ferromagnetic domains with long-range order in semiconducting V-doped WSe2 monolayer synthesized by chemical vapor deposition are reported. Ferromagnetic order is manifested using magnetic force microscopy up to 360 K, while retaining high on/off current ratio of ≈105 at 0.1% V-doping concentration. The V-substitution to W sites keeps a V-V separation distance of 5 nm without V-V aggregation, scrutinized by high-resolution scanning transmission electron microscopy. More importantly, the ferromagnetic order is clearly modulated by applying a back-gate bias. The findings open new opportunities for using 2D transition metal dichalcogenides for future spintronics.
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Affiliation(s)
- Seok Joon Yun
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Doan Manh Ha
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Kirandeep Singh
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Thanh Luan Phan
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Wooseon Choi
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Young‐Min Kim
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
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Kim YR, Phan TL, Shin YS, Kang WT, Won UY, Lee I, Kim JE, Kim K, Lee YH, Yu WJ. Unveiling the Hot Carrier Distribution in Vertical Graphene/h-BN/Au van der Waals Heterostructures for High-Performance Photodetector. ACS Appl Mater Interfaces 2020; 12:10772-10780. [PMID: 32013378 DOI: 10.1021/acsami.9b19904] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Graphene is one of the most promising materials for photodetectors due to its ability to convert photons into hot carriers within approximately 50 fs and generate long-lived thermalized states with lifetimes longer than 1 ps. In this study, we demonstrate a wide range of vertical photodetectors having a graphene/h-BN/Au heterostructure in which an hexagonal boron nitride (h-BN) insulating layer is inserted between an Au electrode and graphene photoabsorber. The photocarriers effectively tunnel through the small hole barrier (1.93 eV) at the Au/h-BN junction while the dark carriers are highly suppressed by a large electron barrier (2.27 eV) at the graphene/h-BN junction. Thus, an extremely low dark current of ∼10-13 A is achieved, which is 8 orders of magnitude lower than that of graphene lateral photodetector devices (∼10-5 A). Also, our device displays an asymmetric photoresponse behavior due to photothermionic emission at the graphene/h-BN and Au/h-BN junctions. The asymmetric behavior generates additional thermal carriers (hot carriers) to enable our device to generate photocurrents that can overcome the Schottky barrier. Furthermore, our device shows the highest value of the Iph/Idark ratio of ∼225 at 7 nm thick h-BN insulating layer, which is 3 orders of magnitude larger than that of the previously reported graphene lateral photodetectors without any active materials. In addition, we achieve a fast response speed of 12 μs of rise time and 5 μs of fall time, which are about 100 times faster than those of other graphene integrated photodetectors.
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Affiliation(s)
- Young Rae Kim
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Yong Seon Shin
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Won Tae Kang
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ui Yeon Won
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ilmin Lee
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ji Eun Kim
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kunnyun Kim
- Korea Electronics Technology Institute, Seongnam 13509, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
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10
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Phan TL, Yu WJ. CVD-Grown Carbon Nanotube Branches on Black Silicon Stems for Ultrahigh Absorbance in Wide Wavelength Range. Sci Rep 2020; 10:3441. [PMID: 32115574 PMCID: PMC7049560 DOI: 10.1038/s41598-020-60580-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 02/11/2020] [Indexed: 11/09/2022] Open
Abstract
We report a black silicon-carbon nanotube (bSi-CNT) hybrid structure for ultrahigh absorbance at wide spectral range of wavelength (300-1200 nm). CNTs are densely grown on entire bSi stems by chemical vapor deposition (CVD) through uniformly coating Fe catalyst. The bSi-CNT not only increases the surface roughness for enhancing the light suppression, but also allows the absorption of light in a wide wavelength range over the Si band gap (>1000 nm owing to 1.1 eV) due to the small band gap of CNT (0.6 eV). At short wavelength below Si band gap (<1000 nm), the absorbance of bSi-CNT shows average of 98.1%, while bSi shows 89.4%, which is because of high surface roughness of bSi-CNT that enhancing the light trapping. At long wavelength over Si band gap, the absorbance of bSi-CNT was maintained to 96.3% because of the absorption in CNT, while absorbance of bSi abruptly reduces with increase wavelength. Especially, the absorbance of bSi-CNT was showed 93.5% at 1200 nm, which is about 30~90% higher than previously reported bSi. Simple growth of CNTs on bSi can dramatically enhances the absorbance without using any antireflection coating layer. Thus, this study can be employed for realizing high efficiency photovoltaic, photocatalytic applications.
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Affiliation(s)
- Thanh Luan Phan
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Woo Jong Yu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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11
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Fan S, Vu QA, Lee S, Phan TL, Han G, Kim YM, Yu WJ, Lee YH. Tunable Negative Differential Resistance in van der Waals Heterostructures at Room Temperature by Tailoring the Interface. ACS Nano 2019; 13:8193-8201. [PMID: 31260265 DOI: 10.1021/acsnano.9b03342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Vertically stacked two-dimensional van der Waals (vdW) heterostructures, used to obtain homogeneity and band steepness at interfaces, exhibit promising performance for band-to-band tunneling (BTBT) devices. Esaki tunnel diodes based on vdW heterostructures, however, yield poor current density and peak-to-valley ratio, inferior to those of three-dimensional materials. Here, we report the negative differential resistance (NDR) behavior in a WSe2/SnSe2 heterostructure system at room temperature and demonstrate that heterointerface control is one of the keys to achieving high device performance by constructing WSe2/SnSe2 heterostructures in inert gas environments. While devices fabricated in ambient conditions show poor device performance due to the observed oxidation layer at the interface, devices fabricated in inert gas exhibit extremely high peak current density up to 1460 mA/mm2, 3-4 orders of magnitude higher than reported vdW heterostructure-based tunnel diodes, with a peak-to-valley ratio of more than 4 at room temperature. Besides, Pd/WSe2 contact in our device possesses a much higher Schottky barrier than previously reported Cr/WSe2 contact in the WSe2/SnSe2 device, which suppresses the thermionic emission current to less than the BTBT current level, enabling the observation of NDR at room temperature. Diode behavior can be further modulated by controlling the electrostatic doping and the tunneling barrier as well.
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Affiliation(s)
- Sidi Fan
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Korea
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
| | - Quoc An Vu
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Korea
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
| | - Sanghyub Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Korea
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
| | - Thanh Luan Phan
- Department of Electronic and Electrical Engineering , Sungkyunkwan University , Suwon 16419 , Korea
| | - Gyeongtak Han
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
| | - Young-Min Kim
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
| | - Woo Jong Yu
- Department of Electronic and Electrical Engineering , Sungkyunkwan University , Suwon 16419 , Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science , Sungkyunkwan University , Suwon 16419 , Korea
- Department of Energy Science, Department of Physics , Sungkyunkwan University , Suwon 16419 , Korea
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Phan TL, Vu QA, Kim YR, Shin YS, Lee IM, Tran MD, Jiang J, Luong DH, Liao L, Lee YH, Yu WJ. Efficient Gate Modulation in a Screening-Engineered MoS 2/Single-Walled Carbon Nanotube Network Heterojunction Vertical Field-Effect Transistor. ACS Appl Mater Interfaces 2019; 11:25516-25523. [PMID: 31264836 DOI: 10.1021/acsami.9b05335] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this report, a screening-engineered carbon nanotube (CNT) network/MoS2/metal heterojunction vertical field effect transistor (CNT-VFET) is fabricated for an efficient gate modulation independent of the drain voltage. The gate field in the CNT-VFET transports through the empty space of the CNT network without any screening layer and directly modulates the MoS2 semiconductor energy band, while the gate field from the Si back gate is mostly screened by the graphene layer. Consequently, the on/off ratio of CNT-VFET maintained 103 in overall drain voltages, which is 10 times and 1000 times higher than that of the graphene (Gr) VFET at Vsd = 0.1 (ratio = 81.9) and 1 V (ratio = 3), respectively. An energy band diagram simulation shows that the Schottky barrier modulation of CNT/MoS2 contact along the sweeping gate bias is independent of the drain voltage. On the other hand, the gate modulation of Gr/MoS2 is considerably reduced with increased drain voltage because more electrons are drawn into the graphene electrode and screens the gate field by applying a higher drain voltage to the graphene/MoS2/metal capacitor.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Lei Liao
- Key Laboratory for Micro-/Nano-Optoelectronic Devices of the Ministry of Education, School of Physics and Electronics , Hunan University , Changsha 410082 , China
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13
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Caballero-Flores R, Bingham NS, Phan MH, Torija MA, Leighton C, Franco V, Conde A, Phan TL, Yu SC, Srikanth H. Magnetocaloric effect and critical behavior in Pr0.5Sr0.5MnO3: an analysis of the validity of the Maxwell relation and the nature of the phase transitions. J Phys Condens Matter 2014; 26:286001. [PMID: 24945593 DOI: 10.1088/0953-8984/26/28/286001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The Maxwell relation, the Clausius-Clapeyron equation, and a non-iterative method to obtain the critical exponents have been used to characterize the magnetocaloric effect (MCE) and the nature of the phase transitions in Pr0.5Sr0.5MnO3, which undergoes a second-order paramagnetic to ferromagnetic (PM-FM) transition at TC ~ 247 K, and a first-order ferromagnetic to antiferromagnetic (FM-AFM) transition at TN ~ 165 K. We find that around the second-order PM-FM transition, the MCE (as represented by the magnetic entropy change, ΔSM) can be precisely determined from magnetization measurements using the Maxwell relation. However, around the first-order FM-AFM transition, values of ΔSM calculated with the Maxwell relation deviate significantly from those calculated by the Clausius-Clapeyron equation at the magnetic field and temperature ranges where a conversion between the AFM and FM phases occurs. A detailed analysis of the critical exponents of the second-order PM-FM transition allows us to correlate the short-range type magnetic interactions with the MCE. Using the Arrott-Noakes equation of state with the appropriate values of the critical exponents, the field- and temperature-dependent magnetization [Formula: see text] curves, and hence the [Formula: see text] curves, have been simulated and compared with experimental data. A good agreement between the experimental and simulated data has been found in the vicinity of the Curie temperature TC, but a noticeable discrepancy is present for [Formula: see text]. This discrepancy arises mainly from the coexistence of AFM and FM phases and the presence of ferromagnetic clusters in the AFM matrix.
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Affiliation(s)
- R Caballero-Flores
- Department of Physics, University of South Florida, Tampa, FL 33620, USA. Departamento de Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, 41080 Sevilla, Spain. Departamento de Física, Universidad de Oviedo, 33007 Oviedo, Spain
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14
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Phan TL, Sun YK, Vincent R, Cherns D, Yu SC. Diffusion of Mn in ZnO nanowires annealed in air. J Nanosci Nanotechnol 2009; 9:817-820. [PMID: 19441399 DOI: 10.1166/jnn.2009.c031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We studied diffusion of Mn in ZnO nanowires by means of field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence and Raman scattering spectroscopy. The Mn-diffused samples were prepared by covering synthesized ZnO nanowires with a Mn chip and then annealing at temperatures between 200 and 1000 degrees C for 1 h in air. Microstructural analyses, and photoluminescence and Raman studies revealed that Mn atoms started diffusing in ZnO nanowires at 800 degrees C. The annealing-temperature increase up to 1000 degrees C led to a strong diffusion of Mn in the ZnO host lattice, which caused the blueshift of the ultra-violet emission. Concurrently, recored Raman scattering spectra showed some additional Mn-related modes. The origin of these lines was discussed in detail.
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Affiliation(s)
- T L Phan
- Micro- and Nano-Structures Group, H. H. Wills Physics Lab, University of Bristol, Bristol BS8-1TL, UK
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15
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Abstract
As elevated endothelin-1 (ET-1) levels have been reported in systemic inflammatory diseases, the role of ET-1 as a promoter of inflammatory reactions is currently under investigation. The purpose of this study was to investigate the potential influence of ET-1 on systemic vascular pressure and immune function in terms of blood clearance and organ distribution of injected Escherichia coli in a rabbit model. To enable quantification of the clearance process, defined numbers of exogenous E. coli (10(8) cfu) were injected intravenously 60 min after starting the infusion of ET-1 (0.2 microgram kg-1 min-1; n = 9) or after saline infusion (controls, n = 9). Parameters monitored were arterial blood pressure, airway pressure, serum lactate concentrations and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were killed, and tissue samples of liver, kidney, spleen and lung were collected for bacterial counts. ET-1 infusion produced an increase in mean arterial pressure (83.9 +/- 3.9 mmHg vs. 50.1 +/- 4.1 mmHg at 120 min; P < 0.01) associated with higher serum lactate concentrations (12.6 +/- 1.3 vs. 5.4 +/- 0.3 mg dL-1; P < 0.001) and a delayed bacterial elimination from the blood compared with controls. Furthermore, there was increased colonization of the lungs (3.6 +/- 0.5 x 10(3) cfu vs. 745 +/- 120 cfu; P < 0.01), spleen (142.4 +/- 45.4 x 10(3) cfu vs. 227 +/- 5.2 x 10(3) cfu; P < 0.05) and kidney (758 +/- 329 vs. 357 +/- 151 cfu; NS), reflecting a reduced bacterial killing function.
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Affiliation(s)
- J Schmeck
- Department of Anaesthesiology and Intensive Care Medicine, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany
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Day NP, Pham TD, Phan TL, Dinh XS, Pham PL, Ly VC, Tran TH, Nguyen TH, Bethell DB, Nguyan HP, Tran TH, White NJ. Clearance kinetics of parasites and pigment-containing leukocytes in severe malaria. Blood 1996; 88:4694-700. [PMID: 8977263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In tropical areas, where unsupervised use of antimalarial drugs is common, patients with an illness consistent clinically with severe malaria but with negative blood smears pose a management dilemma. Malaria pigment is evident in peripheral blood leukocytes in greater than 90% of patients with severe malaria. To characterize the clearance kinetics of parasitized erythrocytes and malaria pigment-containing leukocytes, sequential peripheral blood and intradermal smears were assessed in 27 adult Vietnamese patients with severe falciparum malaria. The clearance of parasitized erythrocytes and pigment-containing monocytes (PCMs) followed first order kinetics. The elimination of pigment-containing neutrophils (PCNs) was first order initially, but deviated from this when counts were low. Clearance of peripheral blood PCMs (median clearance time, 216 hours; range, 84 to 492 hours) was significantly slower than that of parasitized erythrocytes (median, 96 hours; range, 36 to 168 hours) or PCNs (median, 72 hours; range, 0 to 168 hours; P < .0001). Intradermal PCM clearance times were the longest of all (median, 12 days; range, 6 to 23 days; significantly longer than peripheral blood PCM clearance, P < .001). Twenty-one (88%) patients still had signs, symptoms, or laboratory features of severe malaria after parasite clearance but before phagocyte pigment clearance. Sixteen of the 23 surviving patients (70%; 95% confidence interval, 50% to 87%) still had intraleukocytic malaria pigment on peripheral blood films 72 hours after parasite clearance. Thus, by determining the distribution of malaria pigment in peripheral blood and intradermal phagocytes, the time since effective antimalarial treatment started can be estimated. Microscopy for intraleukocytic pigment is valuable in the differential diagnosis of severe febrile illnesses in malarious areas where uncontrolled use of antimalarial drugs is widespread.
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Affiliation(s)
- N P Day
- Centre for Tropical Diseases, Cho Quan Hospital, Ho Chi Minh City, Vietnam
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