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1.
Nanotechnology ; 28(6): 065701, 2017 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-28035093

RESUMO

Few-layer graphene (FLG) was catalytically formed on vertically aligned diamond nanorods (DNRs) by a high temperature annealing process. The presence of 4-5 layers of FLG on DNRs was confirmed by transmission electron microscopic studies. It enhances the field electron emission (FEE) behavior of the DNRs. The FLG-DNRs show excellent FEE characteristics with a low turn-on field of 4.21 V µm-1 and a large field enhancement factor of 3480. Moreover, using FLG-DNRs as cathode markedly enhances the plasma illumination behavior of a microplasma device, viz not only the plasma current density is increased, but also the robustness of the devices is improved.

2.
Chemistry ; 21(45): 16017-26, 2015 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-26382200

RESUMO

We have designed photodetectors and UV field emitters based on a combination of ZnO nanowires/nanorods (ZNRs) and bilayer diamond films in a metal-semiconductor-metal (MSM) structure. The ZNRs were fabricated on different diamond films and systematic investigations showed an ultra-high photoconductive response from ZNRs prepared on ultrananocrystalline diamond (UNCD) operating at a lower voltage of 2 V. We found that the ZNRs/UNCD photodetector (PD) has improved field emission properties and a reduced turn-on field of 2.9 V µm(-1) with the highest electron field emission (EFE) by simply illuminating the sample with ultraviolet (UV) light. The photoresponse (Iphoto /Idark ) behavior of the ZNRs/UNCD PD exhibits a much higher photoresponse (912) than bare ZNRs (229), ZNRs/nanocrystalline diamond (NCD; 518), and ZNRs/microcrystalline diamond (MCD; 325) under illumination at λ=365 nm. A photodetector with UNCD films offers superior stability and a longer lifetime compared with carbon materials and bare ZNRs. The lifetime stability of the ZNRs/UNCD-based device is about 410 min, which is markedly superior to devices that use bare ZNRs (92 min). The ZNRs/UNCD PD possesses excellent photoresponse properties with improved lifetime and stability; in addition, ZNRs/UNCD-based UV emitters have great potential for applications such as cathodes in flat-panel displays and microplasma display devices.

3.
Small ; 10(1): 179-85, 2014 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-23894092

RESUMO

Enhanced electron field emission (EFE) behavior of a core-shell heterostructure, where ZnO nanorods (ZNRs) form the core and ultrananocrystalline diamond needles (UNCDNs) form the shell, is reported. EFE properties of ZNR-UNCDN core-shell heterostructures show a high emission current density of 5.5 mA cm(-2) at an applied field of 4.25 V µm(-1) , and a low turn-on field of 2.08 V µm(-1) compared to the 1.67 mA cm(-2) emission current density (at an applied field of 28.7 V µm(-1) ) and 16.6 V µm(-1) turn-on field for bare ZNRs. Such an enhancement in the field emission originates from the unique materials combination, resulting in good electron transport from ZNRs to UNCDNs and efficient field emission of electrons from the UNCDNs. The potential application of these materials is demonstrated by the plasma illumination measurements that lowering the threshold voltage by 160 V confirms the role of ZNR-UNCDN core-shell heterostructures in the enhancement of electron emission.


Assuntos
Nanotubos/química , Óxido de Zinco/química , Cristalização , Teste de Materiais , Propriedades de Superfície
4.
Analyst ; 139(4): 778-85, 2014 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-24352298

RESUMO

The electrocatalytic properties of a N2 incorporated diamond nanowire (N-DNW) unmodified electrode towards the oxidation of nicotinamide adenine dinucleotide (NADH) was critically evaluated. The electrochemical behavior of the N-DNW unmodified electrode was examined and compared with that of boron-doped diamond, glassy carbon electrode, and graphite electrodes. The N-DNW electrode had high selectivity and high sensitivity for the differential pulse voltammetric detection of NADH in the presence of ascorbic acid at the lower and stable oxidation potential. Moreover, it exhibited strong stability after prolonged usage. The oxidation peak potential at the N-DNW electrode remained unchanged even after exposure to the solution, followed by washing, drying, and storage in laboratory air for 20 days, with minimization of surface contamination. Therefore, the N-DNW unmodified electrode shows promise for the detection of NADH and is attractive for use in a dehydrogenase based biosensor and other analytical applications.


Assuntos
Técnicas Eletroquímicas/métodos , Eletrodos , NAD/análise , NAD/química , Nanofios , Ácido Ascórbico/química , Técnicas Biossensoriais/métodos , Boro/química , Carbono/química , Diamante/química , Grafite/química , Nitrogênio/química , Oxirredução
5.
Nanoscale Adv ; 5(15): 3871-3878, 2023 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-37496626

RESUMO

The study of tiny-sized particles is beneficial in many ways. This has been the subject of many studies. The development of a tiny-sized particle depends on the attained dynamics of the atoms. In the development process of a tiny-sized particle, gold atoms must deal with different modification behaviors. Photons traveling along the air-solution interface also alter the characteristics of a developing tiny-sized particle. The electronic structures, modification behaviors, and attained dynamics of the atoms mainly contribute toward the development of tiny-sized particles. Energy under the supplied source and the local resulting forces collectively bind gold atoms. Both internally and externally driven dynamics influence the development process of different tiny-sized particles. Atoms in such developed tiny-sized particles do not experience the collective oscillations upon photons traveling along the air-solution interface. In the study of binding atoms, it is essential to consider the roles of both energy and force. Here, the development of tiny particles having different sizes presents a convincing discussion. Nucleating a distorted particle from the non-uniform amalgamation of tiny-sized particles is also discussed.

6.
J Nanosci Nanotechnol ; 11(12): 10710-4, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22408979

RESUMO

This work elucidates the electronic structure, electron field emission and magnetic anisotropic behaviors of single wall carbon nanotubes (SWCNTs) for the spin-electronics device application grown on the La0.66Sr0.33MnO3 (LSMO)/SrTiO3 (STO) substrate. Micro-Raman spectroscopy, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES) were used for the study of electronics structure. The field emission characteristics were studied from the electron field emission current density (J) versus applied electric field (E(A)) from which the turn-on electric field (E(TOE)) was evaluated. The magnetization behaviors are also presented by the M-H hysteresis loop and were obtained by applying the magnetic field in the parallel and perpendicular direction of the CNTs at 305 K and 5 K temperatures. A magnetic measurement shows that the coercivity of the CNTs/LSMO/STO is higher and has hig anisotropic-nature than the composite LSMO/STO that could be the good material for the future possible spin-electronics device applications.

7.
Nanoscale ; 13(15): 7308-7321, 2021 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-33889909

RESUMO

We report a novel versatile method for writing charged areas on diamond nanowire (DNW) surfaces using an atomic force microscopy (AFM) tip. Transmission electron microscopy (TEM) investigations revealed the existence of abundant plate-like diamond aggregates, which were encased in layers of graphite, forming nano-sized diamond-graphite composites (DGCs) on DNW surfaces. These DGCs are the main feature, acting as charge-trapping centers and storing electrostatic charge. A hydrogenation process has been observed effectively enhancing the charge-trapping properties of these DNW materials. The effective charge trapping properties with hydrogenation are ascribed to the disintegration of the DGCs into smaller pieces, with an overall increase in the metallic nanographitic phase fractions in a dielectric diamond matrix. Moreover, the written charge on the surface can be easily modified, re-written, or completely erased, enabling application in diamond-based re-writable electronic devices. However, excessive hydrogenation degrades the charge-trapping properties, which is attributed to the etching of the DGCs from the surface. This study demonstrates the potential importance of a simple hydrogenation process in effective electrostatic charge trapping and storage for diamond related nanocarbon materials and the role of DGCs to further enhance it.

8.
Nanoscale ; 12(18): 10117-10126, 2020 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-32352121

RESUMO

Direct synthesis of a nano-structured carbon hybrid consisting of vertically aligned carbon nanograsses on top of boron-doped nanocrystalline diamond is demonstrated and the carbon hybrid is further applied as an electrode material for the fabrication of supercapacitors. The hybrid film combines the dual advantages of sp2 (carbon nanograss) and sp3 (nanocrystalline diamond) bonded carbon, possessing not only the excellent electrical characteristics of sp2 carbon but also the exceptional electrochemical stability of sp3 carbon. As a result, the specific capacitance of the as-prepared hybrid material reaches up to 0.4 F cm-2, one of the highest reported in diamond-based supercapacitors. The entire electrochemical results exhibit enhanced electron transfer efficiency with remarkable stability of 95% of capacitance retention even after 10 000 cycles.

9.
J Nanosci Nanotechnol ; 9(12): 6799-805, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19908682

RESUMO

This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

10.
ACS Appl Mater Interfaces ; 11(51): 48612-48623, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31794182

RESUMO

Electron emission signifies an important mechanism facilitating the enlargement of devices that have modernized large parts of science and technology. Today, the search for innovative electron emission devices for imaging, sensing, electronics, and high-energy physics continues. Integrating two materials with dissimilar electronic properties into a hybrid material is an extremely sought-after synergistic approach, envisioning a superior field electron emission (FEE) material. An innovation is described regarding the fabrication of a nanostructured carbon hybrid, resulting from the one-step growth of boron-doped nanocrystalline diamond (BNCD) and carbon nanospikes (CNSs) by a microwave plasma-enhanced chemical vapor deposition technique. Spectroscopic and microscopic tools are used to investigate the morphological, bonding, and microstructural characteristics related to the growth mechanism of these hybrids. Utilizing the benefits of both the sharp edges of the CNSs and the high stability of BNCD, promising FEE performance with a lower turn-on field of 1.3 V/µm, a higher field enhancement factor of 6780, and a stable FEE current stability lasting for 780 min is obtained. The microplasma devices utilizing these hybrids as a cathode illustrate a superior plasma illumination behavior. Such hybrid carbon nanostructures, with superb electron emission characteristics, can encourage the enlargement of several electron emission device technologies.

11.
Nanomaterials (Basel) ; 9(10)2019 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-31635101

RESUMO

This paper presents a plasma display device (PDD) based on laser-induced graphene nanoribbons (LIGNs), which were directly fabricated on polyimide sheets. Superior field electron emission (FEE) characteristics, viz. a low turn-on field of 0.44 V/µm and a large field enhancement factor of 4578, were achieved for the LIGNs. Utilizing LIGNs as a cathode in a PDD showed excellent plasma illumination characteristics with a prolonged plasma lifetime stability. Moreover, the LIGN cathodes were directly laser-patternable. Such superior plasma illumination performance of LIGN-based PDDs has the potential to make a significant impact on display technology.

12.
ACS Appl Mater Interfaces ; 11(28): 25388-25398, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31260239

RESUMO

Microstructural evolution of nanocrystalline diamond (NCD) nanoneedles owing to the addition of methane and nitrogen in the reactant gases is systematically addressed. It has been determined that varying the concentration of CH4 in the CH4/H2/N2 plasma is significant to tailor the morphology and microstructure of NCD films. While NCD films grown with 1% CH4 in a CH4/H2/N2 (3%) plasma contain large diamond grains, the microstructure changed considerably for NCD films grown using 5% (or 10%) CH4, ensuing in nanosized diamond grains. For 15% CH4-grown NCD films, a well-defined nanoneedle structure evolves. These NCD nanoneedle films contain sp3 phase diamond, sheathed with sp2-bonded graphitic phases, achieving a low resistivity of 90 Ω cm and enhanced field electron emission (FEE) properties, namely, a low turn-on field of 4.3 V/µm with a high FEE current density of 3.3 mA/cm2 (at an applied field of 8.6 V/µm) and a significant field enhancement factor of 3865. Furthermore, a microplasma device utilizing NCD nanoneedle films as cathodes can trigger a gas breakdown at a low threshold field of 3600 V/cm attaining a high plasma illumination current density of 1.14 mA/cm2 at an applied voltage of 500 V, and a high plasma lifetime stability of 881 min is evidenced. The optical emission spectroscopy studies suggest that the C2, CN, and CH species in the growing plasma are the major causes for the observed microstructural evolution in the NCD films. However, the increase in substrate temperature to ∼780 °C due to the incorporation of 15% CH4 in the CH4/H2/N2 plasma is the key driver resulting in the origin of nanoneedles in NCD films. The outstanding optoelectronic characteristics of these nanoneedle films make them suitable as cathodes in high-brightness display panels.

13.
J Nanosci Nanotechnol ; 8(8): 4141-5, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19049191

RESUMO

Nanocrystalline diamond films prepared by microwave plasma enhanced chemical vapor deposition (MPECVD) were implanted using 110 keV nitrogen ions under fluence ranging from 10(13)-10(14) ions/cm2. Scanning Electron Microscopy (SEM) and Raman spectroscopy were used to analyze the changes in the surface of the films before and after ion implantation. Results show that with nitrogen ion implantation in nanocrystalline diamond film cause to decrease in diamond crystallinity. The field emission measurement shows a sharp increase in current density with increase in dose. The ion implantation also alters the turn on field. It is observed that the structural damage caused by ion implantation plays a significant role in emission behaviour of nanocrystalline diamonds.

14.
J Nanosci Nanotechnol ; 8(8): 4198-201, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19049202

RESUMO

Different forms of diamond have been shown to have qualities as field emission sources. As a consequence, much effort has been focused on both the synthesis of diamond nanostructures to increase the field enhancement factor and understanding the emission mechanism in these nominally insulating materials. In our recent study, we have grown ultrananocrystalline diamond (UNCD) coated nanocrystalline diamond (NCD) tips on NCD films for field emitters. The films were characterized using field emission scanning electron microscopy and Raman spectroscopy to identify the quality of the films. The fabricated different sizes of pyramid tips and their field emission properties are reported. It has been observed that with increase in tip size, the turn on voltage also increases.

15.
ACS Appl Mater Interfaces ; 10(34): 28726-28735, 2018 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-30053374

RESUMO

The present work reports the plasma post treatment (ppt) process that instigates the evolution of granular structure of nanocrystalline diamond (NCD), consequently conducing the enhancement of the electron field emission (EFE) properties. The NCD films contain uniform and nanosized diamond grains (∼20 nm) with negligible thickness for grain boundaries that is distinctly different from the microstructure of ultrananocrystalline (UNCD) films with uniformly sized ultrananodiamond grains (∼5 nm) having relatively thick grain boundaries (∼0.1 nm). The turn-on of the electron field emission (EFE) process occurs at ( E0)NCD = 24.1 V/µm and ( E0)UNCD = 18.6 V/µm for the pristine NCD and UNCD materials, respectively. The granular structure of the starting diamond films largely influenced the microstructure evolution behavior and EFE properties of the materials subject to plasma annealing. The CH4/(Ar-H2) ppt-process leads to formation of a hybrid granular structured diamond (HiDNCD and HiDUNCD) via isotropic conjoining of nanosized diamond grains, whereas the CH4/N2 ppt-process leads to the formation of acicular granular structured diamond films (NNCD and NUNCD) via inducing aeolotropic growth of nanodiamond grains. While both of the HiDNCD and HiDUNCD films contain hybrid granular structure, the HiDUNCD films contain a larger proportion of nanographite phase and result in improved EFE properties, viz. ( E0)HiD-UNCD = 7.7 V/µm and ( E0)HiD-NCD = 12.3 V/µm. In contrast, when the films were CH4/N2 ppt-processed, the acicular diamond grains were formed for NUNCD and NNCD films; however, carbon nanoclusters attached to the diamond grains of NNCD films and the nanographitic layers encasing diamond cores are not crystallized very well, as compared with NUNCD films. Therefore, the NNCD films exhibit slightly inferior EFE properties than the NUNCD films, viz. ( E0)N-UNCD = 5.3 V/µm and ( E0)N-NCD = 11.8 V/µm. The difference in EFE properties for ppt-processed NCD and UNCD films corresponds to the dissimilar granular structure evolution behavior in these films that is, in turn, due to the distinct different microstructure of the pristine NCD and UNCD films.

16.
Sci Rep ; 8(1): 283, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29321546

RESUMO

Improving the tribological properties of materials in ambient and high vacuum tribo-conditions is useful for inter-atmospheric applications. Highly-hydrogenated and less-hydrogenated ultrananocrystalline diamond (UNCD) films with distinct microstructural characteristics were deposited on Ti-6Al-4 V alloy, by optimizing the plasma conditions in the chemical vapor deposition. Both the UNCD films showed less friction coefficient in ambient atmospheric tribo-contact conditions due to the passivation. This provides chemical stability to UNCD films under the tribo-mechanical stressed conditions which limits the transferlayer formation and conversion of UNCD phase into graphitization/amorphization. However, in the high vacuum tribo-conditions, highly-hydrogenated UNCD films showed low friction value which gradually increased to the higher magnitude at longer sliding cycles. The low friction coefficient was indicative of passivation provided by the hydrogen network intrinsically present in the UNCD films. It gradually desorbs and the dangling bonds are progressively activated in the contact regime, leading to a gradual increase in the friction value. In contrast, less-hydrogenated UNCD films do not exhibit low friction regime in high vacuum conditions due to the lack of internal passivation. In this case, the conversion of UNCD to amorphized carbon structure in the wear tracks and amorphous carbon (a-C) tribofilm formation on ball scars were observed.

17.
Nanoscale ; 10(3): 1345-1355, 2018 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-29296984

RESUMO

Carbon nanomaterials such as nanotubes, nanoflakes/nanowalls, and graphene have been used as electron sources due to their superior field electron emission (FEE) characteristics. However, these materials show poor stability and short lifetimes, which prevent their use in practical device applications. The aim of this study was to find an innovative nanomaterial possessing both high robustness and reliable FEE behavior. Herein, a hybrid structure of self-organized multi-layered graphene (MLG)-boron doped diamond (BDD) nanowall materials with superior FEE characteristics was successfully synthesized using a microwave plasma enhanced chemical vapor deposition process. Transmission electron microscopy reveals that the as-prepared carbon clusters have a uniform, dense, and sharp nanowall morphology with sp3 diamond cores encased by an sp2 MLG shell. Detailed nanoscale investigations conducted using peak force-controlled tunneling atomic force microscopy show that each of the core-shell structured carbon cluster fields emits electrons equally well. The MLG-BDD nanowall materials show a low turn-on field of 2.4 V µm-1, a high emission current density of 4.2 mA cm-2 at an applied field of 4.0 V µm-1, a large field enhancement factor of 4500, and prominently high lifetime stability (lasting for 700 min), which demonstrate the superiority of these materials over other hybrid nanostructured materials. The potential of these MLG-BDD hybrid nanowall materials in practical device applications was further illustrated by the plasma illumination behavior of a microplasma device with these materials as the cathode, where a low threshold voltage of 330 V (low threshold field of 330 V mm-1) and long plasma stability of 358 min were demonstrated. The fabrication of these hybrid nanowalls is straight forward and thereby opens up a pathway for the advancement of next-generation cathode materials for high brightness electron emission and microplasma-based display devices.

18.
Nanomaterials (Basel) ; 8(9)2018 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-30149533

RESUMO

Low temperature (350 °C) grown conductive nanocrystalline diamond (NCD) films were realized by lithium diffusion from Cr-coated lithium niobate substrates (Cr/LNO). The NCD/Cr/LNO films showed a low resistivity of 0.01 Ω·cm and excellent field electron emission characteristics, viz. a low turn-on field of 2.3 V/µm, a high-current density of 11.0 mA/cm² (at 4.9 V/m), a large field enhancement factor of 1670, and a life-time stability of 445 min (at 3.0 mA/cm²). The low temperature deposition process combined with the excellent electrical characteristics offers a new prospective for applications based on temperature sensitive materials.

19.
ACS Omega ; 3(8): 9956-9965, 2018 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459124

RESUMO

The impact of lithium-ion implantation and postannealing processes on improving the electrical conductivity and field electron emission (FEE) characteristics of nitrogen-doped nanocrystalline diamond (nNCD) films was observed to be distinctly different from those of undoped NCD (uNCD) films. A high-dose Li-ion implantation induced the formation of electron trap centers inside the diamond grains and amorphous carbon (a-C) phases in grain boundaries for both types of NCD films. Postannealing at 1000 °C healed the defects, eliminated the electron trap centers, and converted the a-C into nanographitic phases. The abundant nanographitic phases in the grain boundaries of the nNCD films as compared to the uNCD films made an interconnected path for effectual electron transport and consequently enhanced the FEE characteristics of nNCD films.

20.
J Mater Chem B ; 5(20): 3706-3717, 2017 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-32264059

RESUMO

Thin ultra-nanocrystalline diamond (UNCD) films were evaluated for their use as encapsulating coatings for long-term implantable microchips. The ex vivo hermetic properties of UNCD coatings of various thicknesses and their reaction with tissues in vivo were investigated. Leakage current tests showed that the ∼300 nm thick coatings grown on microchips in (1% H2) Ar/CH4 plasma for 2 hours rendered the surface electrochemically inactive, i.e., the microchips showed an extremely low leakage current density (1.3 × 10-4 A cm-2 at ±5 V). The tests simulate the human body environment ex vivo. Six months after the implantation of the chips in mice, the leakage current density of the thin O-UNCD-coated chips was approximately 7.76 × 10-5 A cm-2 at ±5 V, which is lower than that of chips with a UNCD coating of 1.53 µm thickness deposited for 12 hours (1.71 × 10-4 A cm-2 at ±5 V). These results indicate that the thin coatings can effectively protect the implant from degradation in vivo. Moreover, the relationship between the surface properties of the carbon-based implants and the foreign-body response they elicit was established. Our results strongly indicate that the formation of a fibrous capsule surrounding the implants depend on the surface features of the implants (i.e., roughness, surface area, surface energy, and amount of absorbed fibrinogen) and on the amount of cytokines or chemokines secreted by the host through acute and chronic foreign-body reactions. Finally, oxygen-terminated UNCDs are promising candidates for use as encapsulating coatings without any additional surface modification or functionalization. They exhibit good bioinertness and hermeticity, thus contributing to the direct long-term protection of implantable microelectronic devices from chemical attack by bodily fluids in a physiological environment.

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