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Debela TT, Lim YR, Seo HW, Kwon IS, Kwak IH, Park J, Cho WI, Kang HS. Two-Dimensional WS 2@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular Dynamics Simulations. ACS Appl Mater Interfaces 2018; 10:37928-37936. [PMID: 30360106 DOI: 10.1021/acsami.8b10133] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
As promising candidates for anode materials in lithium ion batteries (LIB), two-dimensional tungsten disulfide (WS2) and WS2@(N-doped) graphite composites were synthesized, and their electrochemical properties were comprehensibly studied in conjunction with calculations. The WS2 nanosheets, WS2@graphite, and WS2@N-doped graphite (N-graphite) exhibit outstanding cycling performance with capacities of 633, 780, and 963 mA h g-1, respectively. To understand their lithium storage mechanism, first-principles calculations involving a series of ab initio NVT- NPT molecular dynamics simulations were conducted. The calculated discharge curves for amorphous phase are well matched with the experimental ones, and the capacities reach 620, 743, and 915 mA h g-1 for WS2, WS2@graphite, and WS2@N-graphite, respectively. The large capacities of the two composites can be attributed to the tendency of W and Li atoms to interact with graphite, suppressing the formation of W metal clusters. In the case of WS2@N-graphite, vigorous amorphization of the N-graphite enhances the interaction of W and Li atoms with the fragmented N-graphite in such a way that unfavorable Li-W repulsion is avoided at very early stage of lithiation. As a result, the volume expansion in WS2@graphite and WS2@N-graphite is calculated to be remarkably small (only 6 and 44%, respectively, versus 150% for WS2). Therefore WS2@(N-)graphite composites are expected to be almost free of mechanical pulverization after repeated cycles, which makes them promising and excellent candidates for high-performance LIBs.
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Affiliation(s)
| | - Young Rok Lim
- Department of Chemistry , Korea University , Sejong 339-700 , Republic of Korea
| | - Hee Won Seo
- Department of Chemistry , Korea University , Sejong 339-700 , Republic of Korea
| | - Ik Seon Kwon
- Department of Chemistry , Korea University , Sejong 339-700 , Republic of Korea
| | - In Hye Kwak
- Department of Chemistry , Korea University , Sejong 339-700 , Republic of Korea
| | - Jeunghee Park
- Department of Chemistry , Korea University , Sejong 339-700 , Republic of Korea
| | - Won Il Cho
- Center for Energy Convergence , Korea Institute of Science and Technology , Seoul 136-791 , Republic of Korea
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Lim YR, Shojaei F, Park K, Jung CS, Park J, Cho WI, Kang HS. Arsenic for high-capacity lithium- and sodium-ion batteries. Nanoscale 2018; 10:7047-7057. [PMID: 29616277 DOI: 10.1039/c8nr00276b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report arsenic (As) as a promising alternative to graphite anode materials in lithium- and sodium-ion batteries (LIBs and SIBs). The electrochemical properties of the As/carbon nanocomposite for both LIBs and SIBs were investigated using experimental and theoretical approaches. The LIBs showed excellent cycling performance, with a reversible capacity of 1306 mA h g-1 (after 100 cycles), which is much higher than that of Li3As (1072 mA h g-1). In the corresponding SIBs, the measured reversible capacity was 750 mA h g-1 (after 200 cycles), which is lower than that of Na3As. Extensive first-principles calculations were performed employing a structure prediction method for crystalline LixAs and NaxAs (x = 1-6) phases, as well as ab initio molecular dynamics simulations for their amorphous phases. In good agreement with the experimental LIB data, our calculations successfully predict the discharge capacity versus voltage curves, showing that the capacity of the amorphous phase reaches up to that of Li4As. In contrast, the SIB exhibited difficulty in reaching the predicted capacity (x = 3.5), probably due to significant volume expansion. Comparison of the theoretical discharge curves with the experimental data provides valuable information for the development of high-performance LIBs and SIBs.
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Affiliation(s)
- Young Rok Lim
- Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
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Seow JG, Lim YR, Shelat VG. Low serum albumin may predict the need for gastric resection in patients with perforated peptic ulcer. Eur J Trauma Emerg Surg 2017; 43:293-298. [PMID: 27074924 DOI: 10.1007/s00068-016-0669-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 04/01/2016] [Indexed: 02/05/2023]
Abstract
PURPOSE Perforated peptic ulcer (PPU) is a common surgical emergency and treatment involves omental patch repair (PR). Gastric resection (GR) is reserved for difficult pathologies. We audit the outcomes of GR at our institution and evaluate the pre-operative factors predicting the need for GR. METHODS This is a single-institution, retrospective study of patients with PPU who underwent surgery from 2004 to 2012. Demographics, clinical presentation and intra-operative findings were studied to identify factors predicting the need for GR in PPU. An audit of clinical outcomes and mortality for all patients with GR is reported. RESULTS 537 (89.6 %) patients underwent PR and 62 (10.4 %) patients GR. Old age (p < 0.0001), female sex (p = 0.0123), non-steroidal anti-inflammatory drugs (NSAIDs) usage (p = 0.0008), previous history of peptic ulcer disease (PUD) (p = 0.0159), low hemoglobin (p < 0.0001), low serum albumin (p < 0.0001), high serum creatinine (p = 0.0030), high urea (p = 0.0006) and large ulcer size (p < 0.0001) predict the need for GR. On multivariate analysis only low serum albumin (OR 5.57, 95 % CI 1.56-19.84, p = 0.008) predicted the need for GR. The presence of Helicobacter pylori infection was protective against GR (OR 0.25, 95 %CI 0.14-0.44, p < 0.0001). Morbidity and mortality of GR was 27.7 and 24.2 %, respectively. CONCLUSION GR is needed in one in ten cases of PPU. Low serum albumin predicted the need for GR on multivariate analysis. Morbidity and mortality of GR remains high.
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Affiliation(s)
- J G Seow
- Department of General Surgery, Tan Tock Seng Hospital, 308433, Singapore, Singapore
| | - Y R Lim
- Department of General Medicine, Tan Tock Seng Hospital, Singapore, Singapore
| | - V G Shelat
- Department of General Surgery, Tan Tock Seng Hospital, 308433, Singapore, Singapore.
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Lee JA, Lim YR, Jung CS, Choi JH, Im HS, Park K, Park J, Kim GT. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy. Nanotechnology 2016; 27:425711. [PMID: 27640642 DOI: 10.1088/0957-4484/27/42/425711] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.
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Affiliation(s)
- Jung Ah Lee
- Department of Chemistry, Korea University, Sejong 30019, Korea
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Kwak IH, Im HS, Jang DM, Kim YW, Park K, Lim YR, Cha EH, Park J. CoSe₂ and NiSe₂ Nanocrystals as Superior Bifunctional Catalysts for Electrochemical and Photoelectrochemical Water Splitting. ACS Appl Mater Interfaces 2016; 8:5327-34. [PMID: 26848805 DOI: 10.1021/acsami.5b12093] [Citation(s) in RCA: 189] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Catalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) are central to key renewable energy technologies, including fuel cells and water splitting. Despite tremendous effort, the development of low-cost electrode catalysts with high activity remains a great challenge. In this study, we report the synthesis of CoSe2 and NiSe2 nanocrystals (NCs) as excellent bifunctional catalysts for simultaneous generation of H2 and O2 in water-splitting reactions. NiSe2 NCs exhibit superior electrocatalytic efficiency in OER, with a Tafel slope (b) of 38 mV dec(-1) (in 1 M KOH), and HER, with b = 44 mV dec(-1) (in 0.5 M H2SO4). In comparison, CoSe2 NCs are less efficient for OER (b = 50 mV dec(-1)), but more efficient for HER (b = 40 mV dec(-1)). It was found that CoSe2 NCs contained more metallic metal ions than NiSe2, which could be responsible for their improved performance in HER. Robust evidence for surface oxidation suggests that the surface oxide layers are the actual active sites for OER, and that CoSe2 (or NiSe2) under the surface act as good conductive layers. The higher catalytic activity of NiSe2 is attributed to their oxide layers being more active than those of CoSe2. Furthermore, we fabricated a Si-based photoanode by depositing NiSe2 NCs onto an n-type Si nanowire array, which showed efficient photoelectrochemical water oxidation with a low onset potential (0.7 V versus reversible hydrogen electrode) and high durability. The remarkable catalytic activity, low cost, and scalability of NiSe2 make it a promising candidate for practical water-splitting solar cells.
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Affiliation(s)
- In Hye Kwak
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
| | - Hyung Soon Im
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
| | - Dong Myung Jang
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
| | - Young Woon Kim
- Graduate School of Green Energy Engineering, Hoseo University , Asan 336-795, Korea
| | - Kidong Park
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
| | - Young Rok Lim
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
| | - Eun Hee Cha
- Graduate School of Green Energy Engineering, Hoseo University , Asan 336-795, Korea
| | - Jeunghee Park
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
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Abstract
FeP and FeP2nanowires exhibit excellent electrocatalytic abilities toward hydrogen evolution from water splitting.
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Affiliation(s)
- Chang Yong Son
- Department of Chemistry
- Korea University
- Jochiwon 339-700
- Korea
| | - In Hye Kwak
- Department of Chemistry
- Korea University
- Jochiwon 339-700
- Korea
| | - Young Rok Lim
- Department of Chemistry
- Korea University
- Jochiwon 339-700
- Korea
| | - Jeunghee Park
- Department of Chemistry
- Korea University
- Jochiwon 339-700
- Korea
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Lim YR, Lim S, Park J, Cho WI, Lim SH, Cha EH. Comparative Cycling Performance of Zn<sub>2</sub>GeO<sub>4</sub> and Zn<sub>2</sub>SnO<sub>4</sub> Nanowires as Anodes of Lithium- and Sodium Ion Batteries. Journal of the Korean Electrochemical Society 2015. [DOI: 10.5229/jkes.2015.18.4.161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
SnxGe1−xS, SnxGe1−xSe, GeSxSe1−x, and SnSxSe1−x alloy nanocrystals were synthesized by novel gas-phase laser photolysis. Their composition-dependent lattice parameters and band gap were thoroughly characterized. The SnxGe1−xS and SnSxSe1−x nanocrystals exhibit higher photoconversion efficiency as compared with the end members.
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Affiliation(s)
- Hyung Soon Im
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Yoon Myung
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Kidong Park
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Chan Su Jung
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Young Rok Lim
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Dong Myung Jang
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Jeunghee Park
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
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Jang DM, Im HS, Back SH, Park K, Lim YR, Jung CS, Park J, Lee M. Laser-induced graphitization of colloidal nanodiamonds for excellent oxygen reduction reaction. Phys Chem Chem Phys 2014; 16:2411-6. [DOI: 10.1039/c3cp54039a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Abstract
Complete composition-tuned SnxGe1−xS alloy nanocrystals exhibit excellent cycling performances in lithium ion batteries, with the greatest rate capability for Sn-rich compositions.
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Affiliation(s)
- Young Rok Lim
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Hyung Soon Im
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Yong Jae Cho
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Jeunghee Park
- Department of Chemistry
- Korea University
- Jochiwon 339-700, Korea
| | - Eun Hee Cha
- Department of Pharmaceutical Engineering
- Hoseo University
- Chungnam 336-795, Korea
| | - Won Il Cho
- Center for Energy Convergence
- Korea Institute of Science and Technology
- Seoul 136-791, Korea
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Im HS, Cho YJ, Lim YR, Jung CS, Jang DM, Park J, Shojaei F, Kang HS. Phase evolution of tin nanocrystals in lithium ion batteries. ACS Nano 2013; 7:11103-11111. [PMID: 24195495 DOI: 10.1021/nn404837d] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Sn-based nanostructures have emerged as promising alternative materials for commercial lithium-graphite anodes in lithium ion batteries (LIBs). However, there is limited information on their phase evolution during the discharge/charge cycles. In the present work, we comparatively investigated how the phases of Sn, tin sulfide (SnS), and tin oxide (SnO2) nanocrystals (NCs) changed during repeated lithiation/delithiation processes. All NCs were synthesized by a convenient gas-phase photolysis of tetramethyl tin. They showed excellent cycling performance with reversible capacities of 700 mAh/g for Sn, 880 mAh/g for SnS, and 540 mAh/g for SnO2 after 70 cycles. Tetragonal-phase Sn (β-Sn) was produced upon lithiation of SnS and SnO2 NCs. Remarkably, a cubic phase of diamond-type Sn (α-Sn) coexisting with β-Sn was produced by lithiation for all NCs. As the cycle number increased, α-Sn became the dominant phase. First-principles calculations of the Li intercalation energy of α-Sn (Sn8) and β-Sn (Sn4) indicate that Sn4Li(x) (x ≤ 3) is thermodynamically more stable than Sn8Li(x) (x ≤ 6) when both have the same composition. α-Sn maintains its crystalline form, while β-Sn becomes amorphous upon lithiation. Based on these results, we suggest that once α-Sn is produced, it can retain its crystallinity over the repeated cycles, contributing to the excellent cycling performance.
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Affiliation(s)
- Hyung Soon Im
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
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Cho YJ, Im HS, Kim HS, Myung Y, Back SH, Lim YR, Jung CS, Jang DM, Park J, Cha EH, Cho WI, Shojaei F, Kang HS. Tetragonal phase germanium nanocrystals in lithium ion batteries. ACS Nano 2013; 7:9075-9084. [PMID: 24020628 DOI: 10.1021/nn403674z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Various germanium-based nanostructures have recently demonstrated outstanding lithium ion storage ability and are being considered as the most promising candidates to substitute current carbonaceous anodes of lithium ion batteries. However, there is limited understanding of their structure and phase evolution during discharge/charge cycles. Furthermore, the theoretical model of lithium insertion still remains a challenging issue. Herein, we performed comparative studies on the cycle-dependent lithiation/delithiation processes of germanium (Ge), germanium sulfide (GeS), and germanium oxide (GeO2) nanocrystals (NCs). We synthesized the NCs using a convenient gas phase laser photolysis reaction and attained an excellent reversible capacity: 1100-1220 mAh/g after 100 cycles. Remarkably, metastable tetragonal (ST12) phase Ge NCs were constantly produced upon lithiation and became the dominant phase after a few cycles, completely replacing the original phase. The crystalline ST12 phase persisted through 100 cycles. First-principles calculations on polymorphic lithium-intercalated structures proposed that the ST12 phase Ge12Lix structures at x ≥ 4 become more thermodynamically stable than the cubic phase Ge8Lix structures with the same stoichiometry. The production and persistence of the ST12 phase can be attributed to a stronger binding interaction of the lithium atoms compared to the cubic phase, which enhanced the cycling performance.
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Affiliation(s)
- Yong Jae Cho
- Department of Chemistry, Korea University , Jochiwon 339-700, Korea
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Im HS, Myung Y, Cho YJ, Kim CH, Kim HS, Back SH, Jung CS, Jang DM, Lim YR, Park J, Ahn JP. Facile phase and composition tuned synthesis of tin chalcogenide nanocrystals. RSC Adv 2013. [DOI: 10.1039/c3ra40869h] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Cho YJ, Kim CH, Im HS, Myung Y, Kim HS, Back SH, Lim YR, Jung CS, Jang DM, Park J, Lim SH, Cha EH, Bae KY, Song MS, Cho WI. Germanium–tin alloy nanocrystals for high-performance lithium ion batteries. Phys Chem Chem Phys 2013; 15:11691-5. [DOI: 10.1039/c3cp51366a] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cho YJ, Im HS, Myung Y, Kim CH, Kim HS, Back SH, Lim YR, Jung CS, Jang DM, Park J, Cha EH, Choo SH, Song MS, Cho WI. Germanium sulfide(ii and iv) nanoparticles for enhanced performance of lithium ion batteries. Chem Commun (Camb) 2013; 49:4661-3. [DOI: 10.1039/c3cc41853g] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Baik SY, Cho YJ, Lim YR, Im HS, Jang DM, Myung Y, Park J, Kang HS. Charge-selective surface-enhanced Raman scattering using silver and gold nanoparticles deposited on silicon-carbon core-shell nanowires. ACS Nano 2012; 6:2459-2470. [PMID: 22314252 DOI: 10.1021/nn204797b] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The deposition of silver (Ag) or gold (Au) nanoparticles (NPs) on vertically aligned silicon-carbon (Si-C) core-shell nanowires (NWs) produces sensitive substrates for surface-enhanced Raman spectroscopy (SERS). The undoped and 30% nitrogen (N)-doped graphitic layers of the C shell (avg thickness of 20 nm) induce a higher sensitivity toward negatively (-) and positively (+) charged dye molecules, respectively, showing remarkable charge selectivity. The Ag NPs exhibit higher charge selectivity than the Au NPs. The Ag NPs deposited on p- and n-type Si NWs also exhibit (-) and (+) charge selectivity, respectively, which is higher than that of the Au NPs. The X-ray photoelectron spectroscopy analysis indicates that the N-doped graphitic layers donate more electrons to the metal NPs than the undoped ones. More distinct electron transfer occurs to the Ag NPs than to the Au NPs. First principles calculations of the graphene-metal adducts suggest that the large electron transfer capacity of the N-doped graphitic layers is due to the formation of a N→Ag coordinate bond involving the lone pair electrons of the N atoms. We propose that the more (-) charged NPs on the N-doped graphitic layers prefer the adsorption of (+) charged dyes, enhancing the SERS intensity. The charge selectivity of the Si NW substrates can also be rationalized by the greater electron transfer from the n-type Si to the metal NPs.
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Affiliation(s)
- Sun Young Baik
- Department of Chemistry, Korea University, Jochiwon Chungnam 339-700, Korea
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