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44 results on '"Kunuku, Srinivasu"'

2. Process Verification of Magnetic Ion Embedded Nanodiamonds Using Secondary Ion Mass Spectroscopy

Author

Lin, Bo-Rong, Chen, Chien-Hsu, Kunuku, Srinivasu, Hsiao, Tung-Yuan, Yu, Hung-Kai, Chen, Tzung-Yuang, Chang, Yu-Jen, Liao, Li-Chuan, Chang, Chun-Hsiang, Chen, Fang-Hsin, Niu, Huan, and Lee, Chien-Ping

Subjects
Physics - Applied Physics
Abstract

Ion implantation is used to create magnetic ion embedded nanodiamonds for use in a wide range of biological and medical applications; however, the effectiveness of this process depends heavily on separating magnetic nanodiamonds from non-magnetic ones. In this study, we use secondary ion mass spectrometry to assess the distribution of magnetic ions and verify the success of separation. When applied to a series of iron/manganese embedded nanodiamonds, the sorting tool used in this study proved highly effective in selecting magnetic nanodiamonds. This paper also discusses the major challenges involved in the further development of this technology., Comment: 12 pages, 3 figures

Published
2019

3. Iron Embedded Magnetic Nanodiamonds for in vivo MRI Contrast Enhancement

Author

Lin, Bo-Rong, Chen, Chien-Hsu, Chang, Chun-Hsiang, Kunuku, Srinivasu, Chen, Tzung-Yuang, Hsiao, Tung-Yuan, Yu, Hung-Kai, Chang, Yu-Jen, Liao, Li-Chuan, Chen, Fang-Hsin, Niu, Huan, and Lee, Chien-Ping

Subjects
Physics - Medical Physics, Physics - Biological Physics
Abstract

Although nanodiamonds have long being considered as a potential tool for biomedical research, the practical in vivo application of nanodiamonds remains relatively unexplored. In this paper, we present the first application of in vivo MRI contrast enhancement using only iron embedded magnetic nanodiamonds. MR image enhancement was clearly demonstrated in the rendering of T2-weighted images of mice obtained using an unmodified commercial MRI scanner. The excellent contrast obtained using these nanodiamonds opens the door to the non-invasive in vivo tracking of NDs and image enhancement. In the future, one can apply these magnetic nanodiamonds together with surface modifications to facilitate drug delivery, targeted therapy, localized thermal treatment, and diagnostic imaging., Comment: 19 pages, 6 figures

Published
2019
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4. A New Boron-10 Delivery Agent for Boron Neutron Capture Therapy: Fluorescent Boron-10 Embedded Nanodiamonds

Author

Lin, Bo-Rong, Kunuku, Srinivasu, Chen, Chien-Hsu, Chen, Tzung-Yuang, Hsiao, Tung-Yuan, Chang, Yu-Jen, Liao, Li-Chuan, Niu, Huan, and Lee, Chien-Ping

Subjects
Physics - Biological Physics, Physics - Medical Physics
Abstract

Boron neutron capture therapy is a powerful anti-cancer treatment, the success of which depends heavily on the boron delivery agent. Enabling the real-time tracing of delivery agents as they move through the body is crucial to the further development of boron neutron therapy. In this study, we fabricate highly bio-compatible boron-10 embedded nanodiamonds using physical ion implantation in conjunction with a two-step annealing process. The red fluorescence of the nanodiamonds allows their use in fluorescence microscopy and in vivo imaging systems, thereby making it possible to conduct tracking in real time. The proposed fluorescent boron-10 embedded nanodiamonds, combining optical visibility and boron-10 transport capability, are a promising boron delivery agent suitable for a wide range of biomedical applications., Comment: 13 pages, 4 figures

Published
2018
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5. Fe Doped Magnetic Nanodiamonds Made by Ion Implantation as Contrast Agent for MRI

Author

Lin, Bo-Rong, Chen, Chien-Hsu, Kunuku, Srinivasu, Chen, Tzung-Yuang, Hsiao, Tung-Yuan, Niu, Huan, and Lee, Chien-Ping

Subjects
Physics - Biological Physics, Physics - Applied Physics
Abstract

We report in this paper a new MRI contrast agent based on magnetic nanodiamonds fabricated by Fe ion implantation. The Fe atoms that are implanted into the nanodiamonds are not in direct contact with the outside world, enabling this new contrast agent to be free from cell toxicity. The image enhancement was shown clearly through T2 weighted images. The concentration dependence of the T2 relaxation time gives a relaxivity value that is about seven times that of the regular non-magnetic nanodiamonds. Cell viability study has also been performed. It was shown that they were nearly free from cytotoxicity independent of the particle concentration used. The imaging capability demonstrated here adds a new dimension to the medical application of nanodiamonds. In the future one will be able to combine this capability of magnetic nanodiamonds with other functions through surface modifications to perform drug delivery, targeted therapy, localized thermal treatment and diagnostic imaging at the same time.

Published
2017
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8. Diamond‐Based Supercapacitors with Ultrahigh Cyclic Stability Through Dual‐Phase MnO2‐Graphitic Transformation Induced by High‐Dose Mn‐Ion Implantation.

Author

Deshmukh, Sujit, Kunuku, Srinivasu, Jakobczyk, Pawel, Olejnik, Adrian, Chen, Chien‐Hsu, Niu, Huan, Yang, Bing, Yang, Nianjun, and Bogdanowicz, Robert

Subjects
*ENERGY density, *SUPERCAPACITORS, *ENERGY storage, *ION implantation, *AQUEOUS electrolytes, *OPTICALLY stimulated luminescence, *LITHIUM cells
Abstract

While occasionally being able to charge and discharge more quickly than batteries, carbon‐based electrochemical supercapacitors (SCs) are nevertheless limited by their simplicity of processing, adjustable porosity, and lack of electrocatalytic active sites for a range of redox reactions. Even SCs based on the most stable form of carbon (sp3 carbon/diamond) have a poor energy density and inadequate capacitance retention during long charge/discharge cycles, limiting their practical applications. To construct a SC with improved cycling stability/energy density Mn‐ion implanted (high‐dose; 1015–1017 ions cm−2) boron doped diamond (Mn‐BDD) films have been prepared. Mn ion implantation and post‐annealing process results in an in situ graphitization (sp2 phase) and growth of MnO2 phase with roundish granular grains on the BDD film, which is favorable for ion transport. The dual advantage of both sp2 (graphitic phase) and sp3 (diamond phase) carbons with an additional pseudocapacitor (MnO2) component provides a unique and critical function in achieving high‐energy SC performance. The capacitance of Mn‐BDD electrode in a redox active aqueous electrolyte (0.05 M Fe(CN)63‐/4− + 1 M Na2SO4) is as high as 51 mF cm−2 at 10 mV s−1 with exceptional cyclic stability (≈100% capacitance even after 10 000 charge/discharge cycles) placing it among the best‐performing SCs. Furthermore, the ultrahigh capacitance retention (≈80% retention after 88 000 charge/discharge cycles) in a gel electrolyte containing a two‐electrode configuration shows a promising prospect for high‐rate electrochemical capacitive energy storage applications. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Investigation of the spectral characteristics of silicon-vacancy centers in ultrananocrystalline diamond nanostructures and single crystalline diamond.

Author

Kunuku, Srinivasu, Chen, Yen-Chun, Chen, Chien-Hsu, Kandasami, Asokan, Chang, Wen-Hao, Niu, Huan, Leou, Keh-Chyang, and Lin, I-Nan

Subjects
*NANODIAMONDS, *ION implantation, *DIAMONDS, *SONICATION, *PHONONS, *NANOSTRUCTURES
Abstract

Silicon-vacancy (SiV) centers were produced in single crystalline diamond (SCD) and ultrananocrystalline diamond (UNCD) nanostructures via Si ion implantation or in situ Si doping. SiV-embedded UNCD (SiV-UNCD) was fabricated by both top-down and bottom-up methods. The spectral properties of the SiV centers, including the zero phonon line (ZPL) width and decay time, were investigated in the SCD and UNCD nanostructures. All the SiV-UNCD nanostructures showed bright emission regardless of the preparation method. However, the decay time of the SiV centers was affected by the synthesis procedure. A SiV decay time of τ ∼ 0.19 ns was observed for UNCD nanostructures formed by in situ doping, whereas the SiV decay time was ∼0.43 ns for SiV-UNCD clusters prepared by Si ion implantation into UNCD deposited on Ti/sapphire substrates. The ultrasonication of UNCD clusters on Ti/sapphire pyramids produced bright SiV-UNCD nanoclusters with sizes of ∼50 nm, a ZPL width of 13.5 nm, and a decay time of 0.35 ns, suggesting promising potential in bioimaging applications. SiV-containing SCD (type Ia or type IIa) showed enhanced SiV spectral properties with a ZPL width of 6.08 nm and longer decay time of 1.3 ns. [ABSTRACT FROM AUTHOR]

Published
2020
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12. Secondary ion mass spectrometry to verify the implantation of magnetic ions in nanodiamonds.

Author

Lin, Bo-Rong, Wang, Chiung-Chi, Chen, Chien-Hsu, Kunuku, Srinivasu, Hsiao, Tung-Yuan, Yu, Hung-Kai, Chen, Tzung-Yuang, Chang, Yu-Jen, Liao, Li-Chuan, Chang, Chun-Hsiang, Chen, Fang-Hsin, Niu, Huan, and Lee, Chien-Ping

Subjects
SECONDARY ion mass spectrometry, NANODIAMONDS, MAGNETIC ions, ION implantation, SILICON wafers, IRON ions
Abstract

Ion implantation is used to create nanodiamonds (NDs) with embedded magnetic ions for use in a wide range of biological and medical applications; however, the effectiveness of this process depends heavily on separating magnetic NDs from nonmagnetic ones. In this study, we use secondary ion mass spectrometry to verify the implantation of magnetic ions in NDs and the success of separation. When applied to a series of NDs with embedded iron or manganese ions, the sorting tool used in this study proved highly effective in selecting magnetic NDs. Besides, multienergy ion implantation and precise thickness control of NDs coating on the silicon wafer were suggested to improve this technology. [ABSTRACT FROM AUTHOR]

Published
2019
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16. Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films.

Author

Kunuku, Srinivasu, Ficek, Mateusz, Wieloszynska, Aleksandra, Tamulewicz-Szwajkowska, Magdalena, Gajewski, Krzysztof, Sawczak, Miroslaw, Lewkowicz, Aneta, Ryl, Jacek, Gotszalk, Tedor, and Bogdanowicz, Robert

Subjects
*PHOTOLUMINESCENCE, *MICROWAVE plasmas, *DIAMOND films, *DIAMOND crystals, *X-ray photoelectron spectroscopy, *CHEMICAL vapor deposition, *ATOMIC force microscopy
Abstract

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C ∼ 0.02 with three different B/C doping concentrations of B/C ∼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74â€"4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C ∼ 7500 ppm) have shown the low resistance value ∼9.29 Ω for CVD diamond/SCD IIa, and the resistance value ∼16.55 Ω for CVD diamond/SCD Ib samples. [ABSTRACT FROM AUTHOR]

Published
2022
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17. Iron embedded magnetic nanodiamonds for in vivo MRI contrast enhancement

Author

Lin, Bo-Rong, primary, Chen, Chien-Hsu, additional, Chang, Chun-Hsiang, additional, Kunuku, Srinivasu, additional, Chen, Tzung-Yuang, additional, Hsiao, Tung-Yuan, additional, Yu, Hung-Kai, additional, Chang, Yu-Jen, additional, Liao, Li-Chuan, additional, Chen, Fang-Hsin, additional, Niu, Huan, additional, and Lee, Chien-Ping, additional

Published
2019
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21. Microstructural Effect on the Enhancement of Field Electron Emission Properties of Nanocrystalline Diamond Films by Li-Ion Implantation and Annealing Processes

Author

Sankaran, Kamatchi Jothiramalingam, primary, Yeh, Chien-Jui, additional, Kunuku, Srinivasu, additional, Thomas, Joseph Palathinkal, additional, Pobedinskas, Paulius, additional, Drijkoningen, Sien, additional, Sundaravel, Balakrishnan, additional, Leou, Keh-Chyang, additional, Leung, Kam Tong, additional, Van Bael, Marlies K., additional, Schreck, Matthias, additional, Lin, I-Nan, additional, and Haenen, Ken, additional

Published
2018
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23. Temperature evolution of optical constants and their tuning in silver

Author

S. K. Dash, Kunuku Srinivasu, A.K. Tyagi, and S. Tripura Sundari

Subjects
Chemistry, Fermi level, Analytical chemistry, Physics::Optics, General Chemistry, Molar absorptivity, Condensed Matter Physics, Drude model, Molecular physics, Wavelength, symbols.namesake, D band, Dispersion (optics), Materials Chemistry, symbols, Fermi–Dirac statistics, Refractive index
Abstract

In this study, high temperature spectroscopic ellipsometry is employed to deduce the temperature dependent refractive indices of silver. The thermo-optic coefficients (thermo-refractive: d n /d T , thermo extinction coefficient: d k /d T ) computed from the temperature dependent refractive indices, showed maximum dispersion and sign changes around the L (direct transition from the d band to the Fermi level i.e., L 3 –L′ 2 ( E F )) interband transition. The positive and negative d n /d T shows that tuning of refractive indices is possible by appropriate choice of incident wavelengths (or energies) and temperatures. The dispersion in d n /d T indicates the possibility of silver thin films being used as thermal lens for either converging or diverging purposes. A negative d k /d T for incident energy radiation around the L transition, indicates, increased transmission and decreased attenuation for these energies. The above dispersion of the thermo-optic coefficients are attributed to a natural outcome of the temperature dependent smearing in the Fermi distribution near the L transition and shift of energy levels due to the temperature dependent deformation potential. This paper also reports the experimental temperature dependence of refractive indices of silver corresponding to 632.8 nm, which has hitherto been obtained from a theoretically based Drude model.

Published
2013
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26. The enhancement of the electron field emission behavior of diamond/CNTs materials via the plasma post-treatment process for the applications in triode-type vacuum field emission transistor

Author

Manoharan, Divinah, primary, Chang, Hsin-Tze, additional, Lin, I-Nan, additional, Chang, Ting-Hsun, additional, Hsieh, Ping-Yen, additional, Kunuku, Srinivasu, additional, Leou, Keh-Chyang, additional, Lee, Chi-Young, additional, and Tai, Nyan-Hwa, additional

Published
2016
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27. Hierarchical hexagonal boron nitride nanowall–diamond nanorod heterostructures with enhanced optoelectronic performance

Author

Sankaran, Kamatchi Jothiramalingam, primary, Hoang, Duc Quang, additional, Korneychuk, Svetlana, additional, Kunuku, Srinivasu, additional, Thomas, Joseph Palathinkal, additional, Pobedinskas, Paulius, additional, Drijkoningen, Sien, additional, Van Bael, Marlies K., additional, D'Haen, Jan, additional, Verbeeck, Johan, additional, Leou, Keh-Chyang, additional, Leung, Kam Tong, additional, Lin, I.-Nan, additional, and Haenen, Ken, additional

Published
2016
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42. Bias-Enhanced Nucleation and Growth Processes for Ultrananocrystalline Diamond Films in Ar/CH4Plasma and Their Enhanced Plasma Illumination Properties

Author

Saravanan, Adhimoorthy, Huang, Bohr-Ran, Sankaran, Kamatchi Jothiramalingam, Kunuku, Srinivasu, Dong, Chung-Li, Leou, Keh-Chyang, Tai, Nyan-Hwa, and Lin, I-Nan

Abstract

Microstructural evolution of ultrananocrystalline diamond (UNCD) films in the bias-enhanced nucleation and growth (BEN-BEG) process in CH4/Ar plasma is systematically investigated. The BEN-BEG UNCD films possess higher growth rate and better electron field emission (EFE) and plasma illumination (PI) properties than those of the films grown without bias. Transmission electron microscopy investigation reveals that the diamond grains are formed at the beginning of growth for films grown by applying the bias voltage, whereas the amorphous carbon forms first and needs more than 30 min for the formation of diamond grains for the films grown without bias. Moreover, the application of bias voltage stimulates the formation of the nanographite phases in the grain boundaries of the UNCD films such that the electrons can be transported easily along the graphite phases to the emitting surface, resulting in superior EFE properties and thus leading to better PI behavior. Interestingly, the 10 min grown UNCD films under bias offer the lowest turn-on field of 4.2 V/μm with the highest EFE current density of 2.6 mA/cm2at an applied field of 7.85 V/μm. Such superior EFE properties attained for 10 min bias grown UNCD films leads to better plasma illumination (PI) properties, i.e., they show the smallest threshold field of 3300 V/cm with largest PI current density of 2.10 mA/cm2at an applied field of 5750 V/cm.

Published
2014
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44. Nano-Mechanical Property Studies of Ti1-xAlxN Thin Films.

Author

Jose, Feby, Kunuku, Srinivasu, Ramaseshan, R., Dash, S., and Tyagi, A. K.

Subjects
*ALUMINUM nitride films, *TITANIUM compounds, *MECHANICAL properties of metals, *NANOSTRUCTURED materials, *SUBSTRATES (Materials science), *MAGNETRON sputtering, *CRYSTAL structure
Abstract

Titanium Aluminum Nitride (Ti1-xAlxN) thin films with different Al concentrations (64 & 81%) were deposited on SS substrate by reactive magnetron co-sputtering. GIXRD result shows that it has NaCl type crystal structure. Adhesion strength of Ti1-xAlxN with 81% Al (3 N) is higher than the 64% (1.4 N) because it is softer than the later. The average surface hardness of these films was measured as 34 and 30 GPa, respectively. [ABSTRACT FROM AUTHOR]

Published
2011
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